It's learned that if Robert Downey Jr. didn't do Captain America 3, but maybe an Iron Man 4 instead, "Civil War" would have never happened.
They said to me, ‘If we have you, we can do this, or Cap 3 has to be something else.’ It’s nice to feel needed. And at this point it’s about helping each other, too. I look at it as a competition and I go, ‘Wow, maybe if these two franchises teamed up and I can take even a lesser position, with people I like and directors I respect, maybe we can keep things bumping along.’
Robert Downey Jr. also teases the seed for Civil War is planted in The Avengers 2.
It’s natural to change your views…The main thing to me is, what sort of incident could occur, and what sort of framework could we find Tony in? The clues about where we might find him next are in Ultron. But what would it take for Tony to completely turn around everything he’s stood for? Joss brings this up all the time. It’s kind of weird that these guys would have all these throw downs all over planet Earth and yet when the movie’s over, nobody minds. What would the American government do if this were real? Wouldn’t it be interesting to see Tony doing something you wouldn’t imagine?
In the Marvel Comics Civil War storyline, Iron Man was looked at as more the villain than Captain America; however, Robert Downey Jr. offers and interesting tidbit in that it could be Steve Rogers who is the one more to change his ways than Tony Stark.
The biggest question is, for Chris and for Cap, how do we bring Cap to a place where people go, ‘Man, I never thought I would see such a vast change in Steve.’ After you see Snowpiercer, you’re like, ‘I want to see a little bit of that guy.’
"Captain America: Civil War" has a May 6, 2016 release directed by Anthony and Joe Russo starring Robert Downey Jr. as Iron Man, Chris Evans as Captain America, Scarlett Johansson as Black Widow, Anthony Mackie as Falcon, Sebastian Stan as Winter Soldier and Chadwick Boseman as Black Panther.
The Avengers 2 Trailer: