He added, "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."

Does this mean that audiences would never see another Tony Stark should Downey hang up his repulsor rays? Russo wouldn't give a definitive no.

"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 specter of Robert hanging over it," he hedged. "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."

Iron Man will next appear in Captain America: Civil War, released May 6. Beyond that, his future remains entirely unclear…