From the looks of things, Thor: Ragnarok is the closest to a new Hulk solo movie we’re going to get anytime soon.
Paramount distributed all of the Marvel hero movies until The Avengers in 2012, and Disney’s purchase of Marvel took effect — except for Hulk’s, whose rights Universal had bought back in the 1990s.
And apparently Universal isn’t game to negotiate the rights for a whole solo movie like Sony was for Spider-Man.
Back then, Marvel Entertainment was a private studio, who worked on production with outside distributors to get their movies made.