Iron Man 3 is going to be Robert Downey Jr's fourth turn as Tony Stark (we're not counting that cameo in The Incredible Hulk). How many Iron Man movies does the actor have in him? I'd guarantee he comes back for The Avengers 2, and then...? It's not impossible to believe that Downey taps out after five or six movies*.
What does Marvel do then? There are big plans in place for the Marvel Movie Universe, and I'm sure the company would like to keep Iron Man in that universe. Where do they go when Downey decides he's done it enough? I took the question right to Kevin Feige, president of Marvel Studios, when I sat down with him for a one on one interview. Would they reboot the series if Downey left, I asked, or would it be like (pre-Casino Royale) Bond, where a new guy took the role and nobody said anything?
"I think Bond is a good example. Let’s put it this way: I hope Downey makes a lot of movies for us as Stark. If and when he doesn’t, and I’m still here making these movies, we don’t take him to Afghanistan and have him wounded again. I think we James Bond it."
I mentioned to Feige that it's easier in the world of comics because pen and ink characters can stay the same age forever. That's not a problem for the Movieverse, he said.
"I think [the character] can age with the actor, if the actor stays with it."
With Iron Man that's actually easy - Downey doesn't have to be in the suit at all, he can just lend his voice to those scenes (which I think is basically what's happening at this point anyway, as opposed to the first film, where he spent more time in the actual armor). And that could keep Downey in for an Avengers 3, if his role ends up being a glorified voice over bit. And since Downey will probably be 50 by the time Avengers 2 hits...
By the way, Feige led this answer off with a little riff on reboots. Since I earlier today spread a little Sony gossip about The Amazing Spider-Man, I thought it was only fair to let Feige have his say on the movie:
"I think the term reboot has got to go. I think it’s like after the Star Wars movies nobody likes the idea of prequels, and reboots have turned into the same thing. It means ‘Oh they’ve run out of ideas! It’s bad.’ I’ve seen The Amazing Spider-Man. It’s awesome. It’s totally fresh and unique."
* Actors who get into Marvel movies now sign very binding multiple picture deals. It's unclear what Downey's deal looks like, as he was the guy who came on when The Avengers was just sort of a pipe dream. If he signed a standard Hollywood type deal, he's locked in for three Iron Man movies and that's it.