Edward Norton, who played Bruce Banner/Hulk in the 2008 version of the film, is open to continuing the character in the 2012 Avengers film, according to MTV. Norton said it's just a matter of scheduling:
"I just get very busy. You have to deal with the demands of the moment. I tend to keep my head in the thing I'm doing, and I don't speculate or worry too much about what two or three blocks down the thing is gonna be. I know all these things will reveal themselves and work out or not."
I'll say this--if Marvel didn't require contractually that Norton appear in the Avengers film, then they're idiots. The last thing we need is a third person playing the character inside of a decade.