I called half of this years ago. Latino Review has discovered that The Avengers will, in their big screen debut, be battling The Skrulls. And Loki, for good measure. Loki will use the Cosmic Cube (which is the centerpiece of Captain America: The First Avenger) to summon the alien race to conquer the Earth.
On top of that, Harry Knowles at Ain’t It Cool has learned that a teaser for The Avengers has been shot. Harry thinks this is a teaser trailer, but I’d bet money that it’s a post-credits cameo for Captain America. We’ll see soon enough.