Isaiah 9:7 , Luke 1:33 For the increase to have no end and the kingdom to continue into infinity there must be a continuous supply of human beings. In the new heaven and new Earth with the new Jerusalem, Revelation 21:3 , Revelation 21:24-26 . There will always be human beings and they will have the hope of being in the kingdom of God just as we do now. Remember, the people are ruled over by those who are in the kingdom, and their hope is to be in that kingdom. I imagine that the new heavens may perhaps be such that all the planets out there will be made suitable to support human life so that as the kingdom grows continually there would be a place for the people. Just a thought.