As discussed before, Planet Hulk movie isn't a priority as the film will have too much cgi Hulk and not enough Rufallo, just more reason for people to hate Rufallo as Banner.
"I think what's cool about the Planet Hulk story is it's all Hulk. He's a gladiator, he's fighting all these creatures on another world. Yes, some of those creatures show up in [Guardians of the Galaxy], which makes people think, 'Oh, maybe it could exist.' And maybe it could exist, someday. I don't think that's the first place we would go though for the very reason that you stated, which is, if we were ever able to do a standalone Hulk movie, 60 percent of the fun would be seeing Mark Ruffalo leading a Marvel movie -- and that's what we would do if we ever went down that road."
- Kevin Feige