I feel like it's going to be Pepper, if only for the "All-New, All-Different" aspect of the title. Granted, Vision ain't exactly new, but he's not been on a proper Avengers team for a while, and Sam Wilson definitely isn't new to the Avengers, but he's still riding the wave of being the current Captain America, so there's his "All-New, All-Different" contribution.
Over all, this is shaping up to be a very different-looking Avengers team, even though they will still have versions of Marvel's Trinity (Cap, Iron Man and Thor).
EDIT: Another reason that's probably not Tony in the suit -- the whole team is basically legacy characters. None of them are the original users of their names (except Vision, and even that's debatable).