"But your dead will live; their bodies will rise. You who dwell in the dust, wake up and shout for joy! Your dew is like the dew of the morning; the earth will give birth to her dead." (Isaiah 26:19 NIV) (see Resurrections)
The Lesson To Nicodemus:
"Born Again" As Actual Spirit Beings
Jesus Christ described "born again" not as a state of mind, but as a literal rebirth as an actual spirit being:
"Jesus answered him, "Truly, truly, I say to you, unless one is born anew, he cannot see The Kingdom of God."
"Nicodemus said to Him, "How can a man be born when he is old? Can he enter a second time into his mother's womb and be born?"
"Jesus answered, "Truly, truly, I say to you, unless one is born of water and the Spirit, he cannot enter The Kingdom of God. That which is born of the flesh is flesh, and that which is born of the Spirit is spirit. Do not marvel that I said to you, 'You must be born anew.'"
"The wind blows where it wills, and you hear the sound of it, but you do not know whence it comes or whither it goes; so it is with every one who is born of the Spirit." (John 3:1-8 RSV)
When Will The Kingdom Of God Be Established?
The Kingdom of God will be established at the Return of Jesus Christ, at which time the process of humans truly being "born again" (i.e. resurrected, or transformed if alive that day) will begin:
"And in the days of those kings the God of heaven will set up a kingdom [see The Return Of Jesus Christ] which shall never be destroyed, nor shall its sovereignty be left to another people. It shall break in pieces all these kingdoms and bring them to an end, and it shall stand for ever; just as you saw that a stone was cut from a mountain by no human hand, and that it broke in pieces the iron, the bronze, the clay, the silver, and the gold. A great God has made known to the king what shall be hereafter. The dream is certain, and its interpretation sure." (Daniel 2:44-45 RSV)
When And How Will Humans Be Truly Born Again?
The first resurrection, at the Return of Christ:
"This is the first resurrection. Blessed and holy is he who shares in the first resurrection! Over such the second death has no power, but they shall be priests of God and of Christ, and they shall reign with Him a thousand years." (Revelation 20:5-6 RSV)
The second resurrection, at the end of the 1,000 years:
"And the sea gave up the dead in it, Death and Hades gave up the dead in them, and all were judged by what they had done. Then Death and Hades were thrown into the lake of fire. This is the second death, the lake of fire; and if any one's name was not found written in the book of life, he was thrown into the lake of fire." (Revelation 20:13-15 RSV)
"For behold, the day comes, burning like an oven, when all the arrogant and all evildoers will be stubble; the day that comes shall burn them up, says The Lord of hosts, so that it will leave them neither root nor branch. But for you who fear My Name the sun of righteousness shall rise, with healing in its wings. You shall go forth leaping like calves from the stall. And you shall tread down the wicked, for they will be ashes under the soles of your feet, on the day when I act, says The Lord of hosts." (Malachi 4:1-3 RSV)
Fact Finder: How did Jesus Christ describe world conditions prior to His return?