"There isn’t one in the pipe. No, there’s no plan for a fourth Iron Man."Downey Jr. signed on to be in both Avengers: Age of Ultron and Avengers 3, so if an Iron Man 4 movie does happen, it doesn’t sounds like it will happen until after the third Avengers film, which will be released in 2018.
When the actor was asked if he would “let” another actor play Tony Stark, Downey laughed off the idea,
“I like that the idea is that it would be up to me, like I’m casting director for Marvel.”If an Iron Man 4 movie does happen, Marvel and Disney will have to re-negotiate a contract with Downey Jr., and if they can’t work something out, they already discussed the idea of replacing the actor, which would be weird, but if the studio wants to continue Stark’s story it would be necessary.
The Avengers: Age of Ultron recently wrapped production in the U.K. with director Joss Whedon, and it’s set to be released on May 1st, 2015.