If there's one thing we know about Hollywood, it's that it can't let a franchise be -- even when it's a nicely contained trilogy. Especially when that is the case, actually. It doesn't even have to be as big a property as Iron Man, but now that Iron Man 3 has opened and already has made more than half a billion dollars worldwide, it's a certainty that Iron Man 4 will be produced. Maybe not right away given Marvel Studios' schedule, but someday. Whether Robert Downey Jr. is on board or not.
That's actually something Marvel's Kevin Feige has reportedly stated. He sees a ton more installments in the series' future with different actors taking on the role if necessary, a la James Bond. Or Batman. Any naysayers with the argument that Robert Downey Jr. IS Tony Stark and vice versa just have to remember that we once thought the same thing about Sean Connery and 007 and Michael Keaton and the Caped Crusader (or even Adam West, for the old-timers). Just cast someone with caliber, not someone from the B-list.
Or, maybe they don't even need to replace RDJ. As we see in Iron Man 3 (SPOILERS?), Stark doesn't even need to be in the suits anymore. They're basically remote-controlled robots. Moviegoers don't care about movie stars anymore anyway, right? They just want to see the Iron Man costume flying, fighting and blowing stuff up. Disney could give RDJ a few million for a day's work for bookending sequences or something. The rest of the time it's all Paul Bettany's voice providing exposition for the hollow heroes.
Another option would be to have someone other than Stark take over as Iron Man. James "Rhodey" Rhodes would be the obvious choice, though it's hard to see Don Cheadle carrying a sequel as the lead. Probably because we really don't get to know that character very deeply in the movies. After the climax of Iron Man 3, I'd even prefer Pepper taking the reins, because Gwyneth Paltrow was surprisingly kick-ass and quite sexy in her moments of action.
You know who I bet would love the honor most, though? Happy Hogan (Jon Favreau). Or that kid, who has an even more awesome character name (Harley Keener) and an actor who is already getting used to franchise stardom (Ty Simpkins, who is recently finished shooting Insidious: Chapter 2).
I'm likely not alone in wanting a continuation rather than a reboot, and anyway the overreaching Avengers film franchise likely wouldn't allow for that -- not that it would be unfaithful to the way comic books work to eventually have diverging continuities.
What should Marvel do with the Iron Man franchise if Robert Downey Jr. doesn't return?
Here are some responses received so far via Twitter: