I've always been kinda "meh" on the X-Men films. I'll see them at the cinemas, but it's never as good as Marvel -produced stuff.
Iron Man 2 in the spring, Thor & Captain America for 2011. Ant-Man's been in development hell for a while, but I don't see how they could do an Avengers thing without him. Without a film to set him up, he'd either be reduced to a background character or he'd take too much focus from everybody else.
I think the Avengers movie should have separate parts or chapters within one film -- kinda like Inglourious Basterds or Kill Bill or that one episode of the Simpsons where we got that same day from different points of view.
That way, each chapter could be written and directed by whoever is in charge of each character (say, Favreau for the Iron Man segment, Letterier for the Bruce Banner part) and we'd still get character interaction.
This seems to me the only sensible route they could take. To just have them all on screen... It's more of a risk, I think. And with the budget that'll come from a film like this, risks are something to be avoided. Then again, based on risks, this could be the best thing to happen to superhero movies ever, or the worst thing since Batman & Robin (which I remember liking as a younger man).