Having been asked about recent stand-alone "Hulk" film rumors starring his incarnation of the character, actor Mark Ruffalo took to Twitter to respond:
"A lot of folks have been asking about the Next Hulk. The next time you see my Hulk it will be in the Avengers 2. No plans for stand alone. I am not giving up on another stand alone HULK. But it's not in the works right now. One never knows what the future will bring."
"Just to be totally clear. I did not say there was not going to ever be a stand alone Hulk film. I said there wasn't one in the works now."
Joss Whedon also spoke with Deadline recently about the character, calling it "the most difficult Marvel property" to adapt:
It's always about balance. Is he a monster? Is he a hero? Are you going to root for a protagonist who spends all his time trying to stop the reason you came to the movie from happening? It's always a dance.
I don't think the first two movies nailed it, but I don't envy them the task. It was easier to have him in a group than to build everything around him. I don't think there would be any problem getting a movie together that had enough Banner, even if there was also Hulk.
But if he was only Hulk for the entire movie I think Mark at some point would go, why am I here? I would be less inclined to pursue a storyline where the Hulk is only ever the Hulk.