While we're speculating and talking rumour, Robert Downey Jr is reportedly considering directing, and not just that but science fiction story of his own design.

Frankly it, like the previous story, is severly speculative and looks like it might be out of context, but at least this comes with a healthy comment from Downey himself. From BreakingNews.ie:

He says: "I will direct a movie. It's a big pissing contest and I'll be a monster. I'll probably want to direct something I've written: I've got a killer science fiction idea. I've got the story in my head, kind of like Mozart on ecstasy… it's called The New Math and it's nuts, so cool."

Doesn't sound like anything coming in the near future though, and frankly I'm pleased. I'd rather see him in front of the camera as much as possible because he's a genuinely fantastic actor.