Even Jesus Christ, though he boldly declared himself part of the Godhead, is well known to have failed badly when in all three synoptic gospels he is made to prophesy the imminent coming of the kingdom of God. Truly, I say to you, this generation will not pass away until all these things take place. That generation passed away nearly two thousand years ago. And if one wants to learn about the future, nothing is less revelatory than the Book of Revelation. In the typical New Yorker cartoon of admission into Heaven, we see St. Peter sitting at a table outside the entrance faced with only one or a few prospective candidates for permanent residence in Heaven.
Resurrected bodies are immortal.
Even if only a small percentage of Christians are saved, the total must mount into the millions. How far back salvation went we do not know, since believers are chary of discussing pre-Adamic man. The absurd creation story of Adam and Eve in Genesis was invented very late in real prehistory, well after hominids from Africa, later replaced by Neanderthal and Cromagnon Man, gradually moved into other continents and with great skill drew recognizable animals on the walls of caves. Adam and Eve were needed, however, for the church doctrine of original sin. Adam is supposed by the Bible to be the ancestor of all humans, from whom they inherited a disposition to sin.