Around the 46 second mark there's a bunch of Shield dudes surrounding a cabin with a green glow in it. This makes me hopeful for the Hulk tearing shit up and being the bad guy in this movie.
I saw Cap today. It was awesome. As for your Hulk=Bad Guy theory, I would imagine it will be something like, say, the origin of The Avengers. Where Loki tricks the world into thinking the Hulk is responsible for some great whatever and they Assemble(!) to stop him. Then join forces with him. Then they go out to a swinging groove club with Jan and Hank...
