It's really no surprise that Robert Downey Jr. is going to eventually make a third Iron Man film, he's signed on to star in several Marvel films as the character Tony Stark/Iron Man. The question that people are asking is will it happen before or after The Avengers? An article over on Yahoo! mentions the fact that Downey Jr. is prepared to do a third Iron Man. They say in an article about the film Due Date starring Zack Galifianakis and Downey Jr. that,
Galifianakis said he expects to begin work this fall on the sequel to The Hangover, while Downey said he aims to suit up for a third Iron Man flick.
I'm pretty confident that Iron Man 3 won't happen until after The Avengers is complete. The Avengers is much further along in the production process, and a first draft of the script was recently turned in to Marvel executives. Downey Jr. also has several film projects in the pipeline to keep him busy over the next couple of years, and I don't think he'd have time to make a third Iron Man film before The Avengers even if he wanted to. Somewhere down the line a third Iron Man film will be made and when it is, it will be under the Disney banner.