Hulk was easily the biggest surprise coming out of The Avengers. After the multiple false starts he suffered the studio didn't think he was movie material, but he blew audiences away in the film. So when is Hulk's movie coming? Well, as we've already learned, no time soon. But it is coming. Spoilers are coming too.
Latino Review has dug up some pretty serious points, the first being that we will be seeing a standalone Hulk film after Avengers 2 lands. This Hulk film will be set up in the Avengers sequel when the Hulk is shipped off into space as he is deemed a threat to humanity. This results in a story based off of Greg Pak's Planet Hulk comic, and involves the Hulk kicking ass gladiator style on an alien planet and raising a rebel army.
What this then leads to is the Hulk returning to earth with an army and battling the earth's heroes in Avengers 3. It's just insanely epic enough to work, and I think Marvel could actually pull this off wonderfully. If this is true then Marvel is really going all out in tying the films together and creating a movie universe as robust as their comics.