Re: Kevin Feige says no to another Hulk Movie.
As people have said, Planet Hulk really doesn't fit the MCU. Nobody really wants to banish the Hulk, nor have they for some time. And Banner has *more* control over the Hulk now, not less, to the point where he can actually act as a superhero under sufficiently extreme circumstances. It would really, really come off as out-of-nowhere and unjustified.
The only possible exception would be if it weren't a deliberate banishment, but an *accidental* one, resulting from a science experiment gone bad or such. Make it a bit of a planetary romance where both Banner *and* Hulk have something to do.