Jon Favreau's interview with ET at the premiere for I Love You Man... This is what he had to say:
To Entertainment Tonight -
Favs: The week Iron Man came out was the week I was shooting this film [I Love You Man] so it was a busy week. We are shooting Iron Man 2 in three weeks, we start shooting, we're rehearsing now. Our main cast is all lined up, everbody's deals are signed. Marvel's about to make some announcements and I think everybody is going to be happy when they hear who we got and we're just working really hard to get this movie ready for next summer.
ET: We hear Mickey Rourke, we hear Scarlett Johansson.
Favs: Well, I hear Mickey's been in Russia doing research for a role, I can confirm that, we haven't made any official announcements yet. But I will say there is a Russian villain in our film. Scarlett is somebody I've been wanting to work with for a while, she's a great actor, we've been talking for a while and we haven't announced anything yet but I'll tell you she hadn't screen tested or anything but I met with her and hopefully we'll be getting everything settled so we can make some announcements this week.
Sounds like the stew is cooking.