I don't think Norton could really stop them going ahead with a Hulk storyline. They're already going to have a lot of characters to deal with without Banner's turmoil. If they do use Hulk, I can't imagine we'd see much Banner at all. I think it'd be mostly just Hulk causing devastation and the Avengers having to deal with it.
It’s possible but I would think they’d like to cash in on how well the Hulk movie did. Don’t get me wrong, I would LOVE to see Hulk in the movie, I just think that it’s unlikely to happen at this point. I really hope I’m wrong though.