Do you think that those who make it through the Tribulation and Millennium will enter eternity in their mortal bodies and thus continue to produce children? If so, wouldn’t the earth eventually become overpopulated and thus the need to colonize other planets? I know it sounds wacky, but it has crossed my mind a couple of times.
Some scholars read Rev. 6: 8 to say 1/4th of the world’s population will die in the seal judgments, and a third of those who survive will die in the Trumpet judgments (Rev. 9:15). There’s no prediction given for the bowl judgments but certainly there will be many more casualties. When you add that to the number who will be raptured, it seems likely that only a small percentage of the world’s current population will survive the End Times judgments.
The Bible says that of those who do survive, only believers will be allowed to enter the Millennium (Matt. 25:46). They will populate the Millennial Earth and will reproduce (Isaiah 65:23). The Bible is silent on the nature of life after the Millennium, but I don’t think there will be any mortals in eternity. Therefore it doesn’t appear that overpopulation will be a problem.