Captain Marvel

Alright, I’m going to go ahead and say that this is the best of the possibilities, and maybe the most likely too. We can assume that Tony was heading to Earth before he became stranded, and having seen Nick Fury page her just before he turned to dust, we know that Captain Marvel is flying there too.

It may seem rather coincidental for them to bump into each other, but the fact is that in the MCU, space just isn’t that big a place. Besides, if Marvel want a better explanation, Captain Marvel could always pick up a distress call. Either way, going forward she is likely to be the leader of the MCU, and what better way to introduce her than to have her save the person she’ll be taking over from?