inhabited exoplanets is a theory that many physicists today are seriously discussing. They remain divided on the issue, but if we assume for the sake of discussion that they exist, then to theists, I ask:
Do you believe there would be a different God for each planet, or one God over them all? If the latter, do you think God's values and commands would change from planet to planet, as befitting their fundamental differences? If you believe in an afterlife, would you expect to see souls from other planets there? Or would it be one afterlife per planet? Do we share heaven with little green angels?
Given it is an assumption, which also implies that Christianity is incorrect, then I do not have an answer.
Fact is, if inhabited (and by that we mean intelligent life) then I would not care whether there was one god or millions or none. And the issue of an after life would become an irrelevancy - as if the biblical God does not exist - then we are left with what? A afterlife that is obviously going to be determined not by faith but at worst by good works. Hence - if there is no god - it wont make a bit of difference for me. If it is plurality of gods and being good is a prerequisite - then I still wont have to worry for I am good by most people's definition - and if there is no obvious need to be good - such as some of our religions - then it matters not what I do. Having a belief along any of the other lines simply becomes redundant.
I don't believe there are other intelligent lifeforms in the universe - save for God, his angels and the demons. Perhaps they have their own planet - who knows? But if there are others - and so far - not a whisper - much less in fact than for the existence of God, then they keep very quiet and invisible.