With contracts presumably running out, and the cost of "Avengers" a-listers going up, the longevity of the likes of Robert Downey Jr. and Chris Evans playing characters in the MCU has been called into question.
In an interview with Forbes, Russo remarked, "It’s almost impossible to replace Robert, he’s the biggest movie star in the world. One close up from Robert is worth another actor’s entire performance, he’s incredibly gifted and insanely talented. I think if and when he is done with the character I think you will find that Iron Man might disappear for a while."
He added, "I think the only way that you could reboot that character is to give a generational gap that would allow another actor to at least have a chance to redefine that character without the enormous spectre of Robert hanging over it. There are so many characters in the Marvel universe that can pick up the ball and run without it through the next phase or two before you need to see Iron Man again, frankly."
Starring Chris Evans, Robert Downey Jr., Scarlett Johansson, Anthony Mackie, Sebastian Stan and more, "Captain America: Civil War" opens on May 6, 2016. The first installment in the Russo's Infinity War saga, "Avengers: Infinity War - Part I," hits theaters on May 4, 2018, followed by "Avengers: Infinity War - Part II" on May 3, 2019.