Here's the thing, the original sorcerer supreme explained that they need the stones to not have a split off reality. Loki moved the tesseract though, and he lives, but what about Steve staying in the past? Are those the same changed reality or are there two of them? I mean what if Steven Rogers has children, and what about him not aging? So instead of an old Steve Rogers sitting there on that bench, a young Steve Rogers who slowly watched time pass and spent a life with Peggy sits there. Children optional. Hint: he's the one who gave Pepper a note that Tony would need some extra medical help.

So Pepper Potts carries around a dose of Extremis/nano particles, and using the stones doesn't kill Tony. Pepper/Tony having another child in an optional bid to save their relationship, but surprise, surprise with the return of half the world Pepper Potts is a CEO Again, and it was never going to last. Plus Tony's second life, and newish immortality have put a serious wrench in the works. Damn, he's young again and looks half her age, and a young Tony just being a house husband only holds while the kids are young not to go to school. The man can never not invent let alone more.

Guess which two superheroes wander into a relationship after all the crap they've been through, and then had lives, and wives, and kids, and still find themselves in the End: Together, Ironman, and Captain America. :D