I will split the question into two and deal with the two parts in reverse order.
1. If you haven't been baptized
Jesus didn’t say ‘you only need to be born again to enter the kingdom of God’. What he actually said was:
John 3:3... Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God.
He then clarifies what he means by being born again:
John 3:5... Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God.
The only way that we can be born of water is by total immersion in water. In English this is called baptism.
Jesus was baptised:
Matthew 3:13 Then cometh Jesus from Galilee to Jordan unto John, to be baptized of him.
Jesus insisted on being baptised. Notice the reason he gives:
Matthew 3:15... Suffer it to be so now: for thus it becometh us to fulfil all righteousness. Then he suffered him.
The Pharisees and lawyers who refused baptism are said to have rejected the counsel of God.
Luke 7:30 But the Pharisees and lawyers rejected the counsel of God against themselves, being not baptized of him.
Jesus (via his disciples) baptised more people than John Baptist.
John 3:22 After these things came Jesus and his disciples into the land of Judaea; and there he tarried with them, and baptized. 23 And John also was baptizing in Aenon near to Salim, because there was much water there: and they came, and were baptized.
John 4:1 When therefore the Lord knew how the Pharisees had heard that Jesus made and baptized more disciples than John, 2 (Though Jesus himself baptized not, but his disciples,)
Jesus instructs his disciples:
Mark 16:15... Go ye into all the world, and preach the gospel to every creature. 16 He that believeth and is baptized shall be saved...
When the Jews convicted by Peter’s argument asked what they should do he says:
Acts 2:38... Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins...
They were all baptised:
Acts 2:41 Then they that gladly received his word were baptized: and the same day there were added unto them about three thousand souls.
The Samaritans were baptised:
Acts 8:12 But when they believed Philip preaching the things concerning the kingdom of God, and the name of Jesus Christ, they were baptized, both men and women.
The Ethiopian eunuch was baptised:
Acts 8:35 Then Philip opened his mouth, and began at the same scripture, and preached unto him Jesus. 36 And as they went on their way, they came unto a certain water: and the eunuch said, See, here is water; what doth hinder me to be baptized? 37 And Philip said, If thou believest with all thine heart, thou mayest. And he answered and said, I believe that Jesus Christ is the Son of God. 38 And he commanded the chariot to stand still: and they went down both into the water, both Philip and the eunuch; and he baptized him.
Cornelius and his household having been baptised with the Holy Spirit were still baptised with water at Peter’s command
Acts 10:47 Can any man forbid water, that these should not be baptized, which have received the Holy Ghost as well as we? 48 And he commanded them to be baptized in the name of the Lord...
Lydia of Thyatira was baptised:
Acts 16:15 And when she was baptized, and her household, she besought us, saying, If ye have judged me to be faithful to the Lord, come into my house, and abide there. And she constrained us.
The Philippian gaoler was told:
31... Believe on the Lord Jesus Christ, and thou shalt be saved, and thy house.
And was baptised:
33... and was baptized, he and all his, straightway.
Saul was baptised:
Acts 22:16 And now why tarriest thou? arise, and be baptized, and wash away thy sins, calling on the name of the Lord.
The disciples at Ephesus were re-baptised:
Acts 19:4 Then said Paul, John verily baptized with the baptism of repentance, saying unto the people, that they should believe on him which should come after him, that is, on Christ Jesus. 5 When they heard this, they were baptized in the name of the Lord Jesus.
We have seen above that baptism by immersion in water is necessary for the remission of sins.
By being baptised into Christ, we ‘put on’ Christ.
Galatians 3:27 For as many of you as have been baptized into Christ have put on Christ.
The phrase ‘as many of you’ indicates that all had been baptised for it is manifest that all in the church at Galatia had ‘put on’ Christ.
Paul explains that baptism is also a figure of ‘dying with Christ’.
Romans 6:3 Know ye not, that so many of us as were baptized into Jesus Christ were baptized into his death? 4 Therefore we are buried with him by baptism into death: that like as Christ was raised up from the dead by the glory of the Father, even so we also should walk in newness of life.
It is easy to see that by baptism we are ‘born again’ for we leave behind our old life style and rise again to a new life with all our sins washed away.
Paul goes on to say that by undergoing baptism we are guaranteed resurrection from the dead.
Romans 6:5 For if we have been planted together in the likeness of his death, we shall be also in the likeness of his resurrection:
There are no exceptions to baptism by immersion in water recorded in the New Testament. It is therefore unreasonable to suppose that baptism is no longer required to ‘put on’ Christ.
2. Can you get to heaven?
Notwithstanding the popular belief in heaven-going as a reward for the righteous, the Bible teaches no such thing.
We do not find the promise of heaven-going in the Bible.
The ‘kingdom of heaven’ and the ‘kingdom of God’ are one and the same and the Bible makes clear that this kingdom will be established forever upon the earth, not in heaven.
This is the reason for the request in the ‘Lord’s’ prayer.
Matthew 6:10 Thy kingdom come. Thy will be done in earth, as it is in heaven.
It is the reason why Jesus says:
Matthew 5:5 Blessed are the meek: for they shall inherit the earth.
God says the same through David:
Psalms 37:11 But the meek shall inherit the earth; and shall delight themselves in the abundance of peace.
Psalms 37:22 For such as be blessed of him shall inherit the earth; and they that be cursed of him shall be cut off.
When God created the earth he created it as an eternal habitation for the descendents of Adam.
Psalms 115:16 The heaven, even the heavens, are the LORD’S: but the earth hath he given to the children of men.
God’s purpose is to fill this earth with his glory.
Numbers 14:21 But as truly as I live, all the earth shall be filled with the glory of the LORD.
Habakkuk 2:14 For the earth shall be filled with the knowledge of the glory of the LORD, as the waters cover the sea.
God’s glory will be in the form of men and women raised to the divine nature and made equal unto the angels.
2 Peter 1:4 Whereby are given unto us exceeding great and precious promises: that by these ye might be partakers of the divine nature, having escaped the corruption that is in the world through lust.
Luke 20:36 Neither can they die any more: for they are equal unto the angels; and are the children of God, being the children of the resurrection.
The redeemed will not be going to heaven to be with God; rather God will dwell within men. Paul explains that at the end of the millennial reign God will be ‘all in all’.
1 Corinthians 15:24 Then cometh the end, when he shall have delivered up the kingdom to God, even the Father; when he shall have put down all rule and all authority and power. 25 For he must reign, till he hath put all enemies under his feet. 26 The last enemy that shall be destroyed is death. 27 For he hath put all things under his feet. But when he saith all things are put under him, it is manifest that he is excepted, which did put all things under him. 28 And when all things shall be subdued unto him, then shall the Son also himself be subject unto him that put all things under him, that God may be all in all.
That the kingdom of heaven is an inheritance upon the earth is seen in the promise made to Abraham.
Genesis 13:15 For all the land which thou seest, to thee will I give it, and to thy seed for ever.
In his lifetime Abraham did not receive the inheritance promised.
Acts 7:5 And he gave him none inheritance in it, no, not so much as to set his foot on: yet he promised that he would give it to him for a possession, and to his seed after him, when as yet he had no child.
Isaac and Jacob were also promised an inheritance in the land forever.
Exodus 32:13 Remember Abraham, Isaac, and Israel, thy servants, to whom thou swarest by thine own self, and saidst unto them, I will multiply your seed as the stars of heaven, and all this land that I have spoken of will I give unto your seed, and they shall inherit it for ever.
God promised that he would prolong the lives of those who were faithful in Israel upon the earth forever.
Deuteronomy 4:40 Thou shalt keep therefore his statutes, and his commandments, which I command thee this day, that it may go well with thee, and with thy children after thee, and that thou mayest prolong thy days upon the earth, which the LORD thy God giveth thee, for ever.
The promise is an eternal inheritance upon the earth as seen in Psalm 37.
Psalms 37:18 The LORD knoweth the days of the upright: and their inheritance shall be for ever.
Psalms 37:28 For the LORD loveth judgment, and forsaketh not his saints; they are preserved for ever: but the seed of the wicked shall be cut off.
Psalms 37:29 The righteous shall inherit the land, and dwell therein for ever.
Psalms 37:34 Wait on the LORD, and keep his way, and he shall exalt thee to inherit the land: when the wicked are cut off, thou shalt see it.
Isaiah 60:21 Thy people also shall be all righteous: they shall inherit the land for ever...
Ezekiel 37:25 And they shall dwell in the land that I have given unto Jacob my servant, wherein your fathers have dwelt; and they shall dwell therein, even they, and their children, and their children’s children for ever: and my servant David shall be their prince for ever.
Ezekiel 43:7 And he said unto me, Son of man, the place of my throne, and the place of the soles of my feet, where I will dwell in the midst of the children of Israel for ever, and my holy name, shall the house of Israel no more defile, neither they, nor their kings, by their whoredom, nor by the carcases of their kings in their high places.
Ezekiel 43:9 Now let them put away their whoredom, and the carcases of their kings, far from me, and I will dwell in the midst of them for ever.
The faithful did not receive that which was promised in their lifetime because the promise was to be extended to us.
Hebrews 11:39 And these all, having obtained a good report through faith, received not the promise: 40 God having provided some better thing for us, that they without us should not be made perfect.
The kingdom of heaven that is to be established on the earth is the restored throne of David with its jurisdiction extended to the whole earth. The kingdom is to be established ‘before him’ meaning ‘in his presence’.
2 Samuel 7:16 And thine house and thy kingdom shall be established for ever before thee: thy throne shall be established for ever.
1 Chronicles 17:11 And it shall come to pass, when thy days be expired that thou must go to be with thy fathers, that I will raise up thy seed after thee, which shall be of thy sons; and I will establish his kingdom. 12 He shall build me an house, and I will stablish his throne for ever. 13 I will be his father, and he shall be my son: and I will not take my mercy away from him, as I took it from him that was before thee: 14 But I will settle him in mine house and in my kingdom for ever: and his throne shall be established for evermore.
This was the ‘house of the LORD’ that David looked forward to.
Psalms 23:6 Surely goodness and mercy shall follow me all the days of my life: and I will dwell in the house of the LORD for ever.
Psalms 61:4 I will abide in thy tabernacle for ever: I will trust in the covert of thy wings.
Psalms 68:16 Why leap ye, ye high hills? this is the hill which God desireth to dwell in; yea, the LORD will dwell in it for ever.
Psalms 72:19 And blessed be his glorious name for ever: and let the whole earth be filled with his glory; Amen, and Amen.
Jesus Christ is both son of David and son of God to whom the throne and the everlasting kingdom is promised.
Luke 1:31 And, behold, thou shalt conceive in thy womb, and bring forth a son, and shalt call his name JESUS. 32 He shall be great, and shall be called the Son of the Highest: and the Lord God shall give unto him the throne of his father David: 33 And he shall reign over the house of Jacob for ever; and of his kingdom there shall be no end.
Psalms 45:6 Thy throne, O God, is for ever and ever: the sceptre of thy kingdom is a right sceptre.
Hebrews 1:8 But unto the Son he saith, Thy throne, O God, is for ever and ever: a sceptre of righteousness is the sceptre of thy kingdom.
Psalms 89:29 His seed also will I make to endure for ever, and his throne as the days of heaven.
Isaiah 9:7 Of the increase of his government and peace there shall be no end, upon the throne of David, and upon his kingdom, to order it, and to establish it with judgment and with justice from henceforth even for ever. The zeal of the LORD of hosts will perform this.
God promises through Daniel the setting up of this everlasting kingdom upon the earth.
Daniel 2:44 And in the days of these kings shall the God of heaven set up a kingdom, which shall never be destroyed: and the kingdom shall not be left to other people, but it shall break in pieces and consume all these kingdoms, and it shall stand for ever.
Daniel 7:18 But the saints of the most High shall take the kingdom, and possess the kingdom for ever, even for ever and ever.
Micah 4:7 And I will make her that halted a remnant, and her that was cast far off a strong nation: and the LORD shall reign over them in mount Zion from henceforth, even for ever.
Paul says that the promise to Abraham was that he should be the heir of the world.
Romans 4:13 For the promise, that he should be the heir of the world, was not to Abraham, or to his seed, through the law, but through the righteousness of faith.
Those who have put on Christ through baptism become heirs of the same promise.
Galatians 3:29 And if ye be Christ’s, then are ye Abraham’s seed, and heirs according to the promise.
When we read of the heavenly kingdom in 2 Timothy we cannot suppose that this is a different kingdom to that promised elsewhere. Though it is called a ‘heavenly kingdom’ it is nonetheless established upon the earth (with God’s will being done ‘as in heaven’).
2 Timothy 4:18 And the Lord shall deliver me from every evil work, and will preserve me unto his heavenly kingdom: to whom be glory for ever and ever. Amen.
In Revelation 11:15 the voices speak in heaven but the kingdom is upon the earth.
Revelation 11:15 And the seventh angel sounded; and there were great voices in heaven, saying, The kingdoms of this world are become the kingdoms of our Lord, and of his Christ; and he shall reign for ever and ever.
At the end of the thousand year reign of Christ there will be a final judgment and all who live on afterwards will have the divine nature. God will dwell in them but they will dwell upon the earth. As we have no idea what it will be like to be equal to the angels, we cannot begin to imagine how life will be lived, but it seems reasonable to suppose that where we live will be of no consequence in our relationship with our creator.
Revelation 21:3 And I heard a great voice out of heaven saying, Behold, the tabernacle of God is with men, and he will dwell with them, and they shall be his people, and God himself shall be with them, and be their God. 4 And God shall wipe away all tears from their eyes; and there shall be no more death, neither sorrow, nor crying, neither shall there be any more pain: for the former things are passed away. 5 And he that sat upon the throne said, Behold, I make all things new. And he said unto me, Write: for these words are true and faithful. 6 And he said unto me, It is done. I am Alpha and Omega, the beginning and the end. I will give unto him that is athirst of the fountain of the water of life freely. 7 He that overcometh shall inherit all things; and I will be his God, and he shall be my son.
The hope of those who are baptised by immersion in water into Christ is that of resurrection to eternal life in the kingdom of God upon earth when Jesus Christ returns from heaven.
Those who are not baptised into Christ die without hope of life.
I hope you have found this helpful.
God bless you,