The Daily Beast interviewed Whedon, who said:
The Avengers 2 is on the horizon, and Robert Downey Jr. is technically not signed yet. How crucial is he to the franchise? His Tony Stark is almost Shakespearean.
He is Iron Man. He is Iron Man in the way that Sean Connery was James Bond. I have no intention of making Avengers 2 without him, nor do I think I’ll be called upon to do that. I don’t think it’s in my interest, Marvel’s interest, or his interest, and I think everything will be fine. But I know that this is Hollywood and you roll with things. You have to be ready for the unexpected. But I loved working with Robert, and everybody knows he embodied that role in a way no one else can. The day he was cast, I went up to [Marvel Studios president] Kevin Feige and said, “You brilliant son of a bitch.”