There hasn't been a solo Hulk movie since the 2008 Incredible Hulk film with the reason being Marvel Studios doesn't have the distribution rights.
I suppose Marvel Studios could still do a Hulk movie, but they don't want Universal to distribute it, so there won't be a Hulk movie any time soon.
Of course that doesn't mean the Green Goliath won't be appearing in the MCU as the Hulk returns next month for Thor: Ragnarok.
Cinema Blend recently caught up with Mark Ruffalo while promoting Thor: Ragnarok who offered up the following, in that Thor: Ragnarok, The Avengers: Infinity War and The Avengers 4 is more or less a Hulk trilogy (as it pertains to the character).
So basically, Kevin [Feige] pulled me aside before this, and said, 'If you were gonna do a... if we were going to do a standalone Hulk movie, what would it be?' And I said, 'I think it should be this, this, this, and this and this, and ends up like this.' And he's like, 'I love that. Why don't we do that in the next three movies, starting with Thor 3 and then we go into Avengers 3 and 4.' And I was like, 'That sounds great!' And so we are at the beginning of this arc.
Mark Ruffalo was also asked about Hulk speaking in Thor: Ragnarok, with Ruffalo offering it's a clue to Hulk's future stories in the next Avengers movies.
Hulk speaking is the start to separating of these two individuals, these identities in this split-identity person, and where that's going to end up going. So it was really interesting to me. He's like a baby! He's like a five year old or six year old. So he has the same syntax, he has the same world view, and so it was fun. It's like Chris [Hemsworth] - we all got to reinvent our characters in this.
We see mention of the Hulk and Banner's personalities being split, which is something the MCU has shied away from since the original solo Hulk movies. Since the first Avengers movie, it seemed like the Hulk and Banner weren't that different, which is a different take than the comics (at times) and even the well-known TV show. It's possible they are using The Avengers: Infinity War and The Avengers 4 to set up the Hulk in Marvel's Phase 4 plans... whatever they may be.
Thor: Ragnarok smashes its way into theaters November 3, 2017.