Robert Downey, Jr. was recently on ABC's Nightline and commented that he felt he could play Tony Stark once more. No one could blame him, given the immense popularity of the franchise, as well as the hefty paycheck that will likely come with it. And, since these films earn a staggering amount of money, it's entirely possibly that the studio would be keen on releasing another.
For the time being, fans will have to check him out in the upcoming film "Captain American: Civil War" to get their Iron Man fix. He will also be appearing in the upcoming Spider-Man: Homecoming film.