I really like the theory that the universe is forever expanding and contracting and that one day, the expansion will once again stop and then reverse back into a collapsed state, and along the way, all the grabby aliens that have dominated their region of space will find themselves going from feeling alone in the universe to being neighbors, until they are right on top of each other and battling for existence in the collapse.

And maybe the goal is to figure out how to break out before being squished.