What I think the sequel needs is a deeper story, and not reducing Hulk to a plot device. TIH was a good film, but it had limited sunstance. I think the main reason for this was that we didn't really get into the mind of Banner and the Hulk (the closest we got to this was the cave scene). Some of the deleted scenes would have been perfect to have in the film, and would have provided some substance (I loved the dinner table scene and the one where Banner pours his heart out to Betty at the campus). Also, Hulk needs to be a character in himself. He needs to have a personality. The audience WILL NOT connect to a mute beast with no personality. That's one of the things that Avengers: EMH has gotten right. The Hulk is a character with appeal. He doesn't just show up and smash stuff. He actually has stuff to say about the situation. Now, this could be cheesy in the films if not handled right, but with the right talent, a sequel can work. I really do want a sequel. I love Hulk, and am hoping for a movie that can strike audiences. And let Ruffalo stay Banner. Can we have the same actor for more than one movie, please?
BTW, I'm interested to see WHERE a sequel would pick up, judging that Banner is an ally to SHIELD now and really has no reason to run anymore.