It looks like we might get Planet Hulk Hulk without Planet Hulk, though still in space.
Mark Ruffalo has been doing the rounds for his movie Infinitely Polar Bear (we assume he's playing some kind of CGI bear that discovers an infinity stone... right?), and dropping some hints about Hulk's role in Thor: Ragnarok along the way. In an interview with Aintitcool he finally revealed something fairly big.
"The Banner/Hulk consciousness is beginning to meld a little bit," Ruffalo said. "He's on the run. He's removing himself from humanity altogether." Of course, that goes so far as to take him into space, if he's somehow involved in Asgard and the fall of the "gods" there.
As far as that merger of minds, Ruffalo said it will be interesting to explore.
"Who decided to leave? Was it Banner of Hulk? It's not really in the mythology of Hulk up until that moment to be that conscious and pro-active. It's interesting, right?" he posits. "The comic books have kind of broached the subject, but we're moving away from the traditional Hulk/Banner relationship. We're starting to mess with it a little bit."
In the comic book storyline Planet Hulk, Hulk simply stopped turning back into Banner. The long time as Hulk allowed him to start accessing more and more of Banner's advanced intelligence. The two even had a bit of an agreement over Hulk staying in control on the gladiator planet, which it sounds like may inform his use here.
Incidentally, Craig Kyle is one of the co-writers of the first draft of Thor: Ragnarok, and also co-wrote the Planet Hulk animated film. He and Chris Yost (also a co-writer on Ragnarok) also wrote the Hulk vs. Thor animated film, as well.