Speculation was Favreau has simply worked himself out. He has multiple projects lined up and a new film coming out this summer. Marvel’s new stance on it’s films is really simple, they want them done sooner rather than later. They have steam rolled forward continually no matter what was standing in their way. They got Iron Man made then reboot Hulk. Now they had Iron Man 2 rushed into production followed by Thor, Captain America and Avengers. With rumors of another Hulk movie in the works along with a second Thor film(already?) the studio is just going without hesitation. So maybe Favreau wanted to slow down and they just couldn’t deal. I don’t know but this isn’t good. Marvel needs to make sure they do not mess up like they did with X-men 3 or X-men Origins or either Fantastic Four movies. They need someone who wants to continue the theme the films had. Mandarin needs to be the villain since I believe he was set up in the first film. Remember the terrorist leader with the rings? The guys group was named “The Ten Rings”… It’s perfect! Even though the rumor is IM3 would be set after the avengers and involving multiple characters. Still this news is simply not good, Iron Man was a good example of how to make a solid comic book film.