As discussed elsewhere, I'm sure, Marvel has recently announced major changes in status quo for the Captain America and Thor characters. I've also noticed the return of "Iron Lad" in the upcoming Avengers storyline, and that got me thinking about the inevitability of replacing actors in long-running franchises.
How likely is it that Captain Falcon, Lady Thor, and Iron Lad will be the core of the, say, fifth Avengers film?