Earlier this year, there was much discussion over if Robert Downey, Jr. would return to play Iron Man after Iron Man 3. Downy, Jr. eventually signed a contract to return as Iron Man for Avengers 2 & 3, but it's still unknown if he will do another Iron Man movie.
In an interview with Yahoo to promote Turbo, which is just now being released in the UK, Samuel L. Jackson shared his thoughts on if there could be an Iron Man without Robert Downey, Jr. Jackson comes off as being a little take aback in the interview, but it's probably because he's doing the interview to promote Turbo and instead is being asked about Robert Downey, Jr.
Jackson said, "Robert’s a great guy. We love having him around. He’s an integral character in those stories. [It] wouldn’t have been the same without him. But you know… Marvel is Marvel, things happen. And audiences are fickle too."
"At some point, if Robert decides he’s not going to do it, and they put somebody else inside that Iron suit… you know, it might work," added Jackson. "They changed War Machine, nobody noticed."