What will become of the non-believers who have not come to faith prior to the Second Coming, yet have managed to survive through the Tribulation era while refusing to take the mark? Will these individuals also take part in the repopulating of the planet during the Millennial Era along with the Tribulation Saints, or will they suffer the same fate as those who willingly took the mark, and are part of the antichrist system?
You’re proposing a hypothetical situation that the Bible says will not happen. 2 Thes 2:9-12 says everyone who refuses to love the truth and be saved will perish and God will see that it happens. Rev. 13:8 says everyone on earth whose name has not been written in the Lamb’s book of life will worship the anti-Christ. There will not be anyone left in the”not sure” category during this time.