He was banished from the world until the prophecy of the Elder Scroll that sent him there would be completed.
I can't see him returning without some kind of strange contradiction. Perhaps another Elder Scroll could be read at the Time-Wound, but then again, how to get there at all without the Thu'um?
I'm not entirely educated on the mechanics of the magic used to throw Alduin into the future but to my understanding some dudes in the past threw him into some time tunnel thing and he kida falls out during Skyrim? If thats correct is it at all possible that he could like... fall out early and need a not so gentle push back in =P