Another thing is that, if we did colonize space, we would probably split into another species before long. It is also possible that every planet we colonize would have a different variant of the human specifies. You would definitely see humans evolve for space travel.
And that is from the biological perspective. We could also self-evolve by fusing with machines. Arthur C. Clarke (who was a tremendous visionary) also thought that eventually we would become the equivalent of cyborg spaceships.
Natural selection would continue to operate, but different traits would be more beneficial in various environments.
To me, the only scenarios that don’t seem “reasonable” to some extent are those which require that human nature cease to be human nature. The entire history (and known prehistory) of Earth makes it clear that people are always the same. The range of possible outcomes from any change in environment is limited by the fact that we are what we are.