He signed a six picture deal, not necessarily a deal for six solo Hulk movies. I'm sure he'll be in further Avengers movies, maybe one or two Hulk movies, possibly appearances in a Spider-Man movie or whatever.
I wonder how that would work...three different studios license several different sets of Marvel characters...X-Men and Fantastic Four are Fox, Spider-Man is Sony and Avengers are now Disney (formerly Paramount). Crossing characters between those settings may require some legal wrangling. It would be nice to see the entire Marvel universe under one banner.