Hitflix says they know what happens to the Hulk in the final act of Avengers: Age of Ultron. This could be a rumor, or it could be a spoiler, but if it's true, it has some major ramifications for Phase 3 of the Marvel cinematic universe.
Supposedly, the Hulk will become trapped in a quinjet at the end of Age of Ultron, and shot sent into space, a la the Planet Hulk storyline (although it almost certainly will be a trap engineered by Ultron, and not a massive betrayal by Iron Man, as per the comics). Now, Mark Ruffalo has very recently scoffed at the idea of a Planet Hulk movie, and with good reason, but that doesn't mean that Marvel couldn't or wouldn't still use the idea of sending the Hulk off-planet for a future film.
Hitflix has a theory about where the Hulk could be going:
Here's where I'd wager his spaceship is headed: wherever the Guardians of the Galaxy are located. If I was a betting man, I'd say there will be no Hulk solo film as part of Phase Three. Instead, Banner's ship will take him to another planet, where he will end up meeting the Guardians and having an adventure with them. Hulk will definitely come out to play a few times. I suspect we'll see some sequences that very much feel like they're part of the Planet Hulk story, but that the larger story will be about the Guardians finding a way to get Banner home, only to end up going with him. That would move a big piece of the puzzle into place to get Thanos looking back at the Earth in time for the third "Avengers" film.
Hmm. It's plausible, and sending the Hulk to hang with the Guardians would be a great way to tie them more directly to the Marvel movie-verse and bring them into Avengers 3. Besides, Marvel hasn't seemed interested in doing another Hulk solo at all, but combining Planet Hulk with the Guardians of the Galaxy would take care of that rather nicely. And I think it still tracks with Ruffalo's denial that Marvel is doing Planet Hulk, since technically it would be a Guardians of the Galaxy film, although Ruffalo would have to know he's being extremely disingenuous. It seems like something he'd do.
But I'm not sure how I feel about this. Imagining Mark Ruffalo's Bruce Banner hanging out with Star-Lord just feels wrong somehow. Maybe we could just have a Science Bros. movie instead?