Hulk Is An Easier Character To Keep Around Than Captain America Or Iron Man
Hulk's relative lack of solo movies has added longevity to the character in ways that go beyond Ruffalo's contract with the studio. Like other "supporting Avengers" - Black Widow and Hawkeye being the obvious examples - Hulk still has a great deal of unexplored potential within the MCU. Iron Man has enjoyed three solo movies, an Avengers movie largely based around the consequences of his arrogance (Age of Ultron), a supporting role in Spider-Man: Homecoming, and what was basically a co-lead role in Captain America: Civil War. He was also one of the most prominent superheroes in Avengers: Infinity War, and is poised for a similarly crucial role in Avengers 4. At this point, Marvel Studios would need to get seriously creative with Tony Stark to avoid his character arcs starting to feel stale.
By contrast, we've barely scratched the surface of Hulk's potential in the movies. Between all the various threats to the planet, Bruce's romance with Black Widow has been sidelined to the point of near non-existence, with the two sharing little more than a greeting in Avengers: Infinity War. Admittedly that particular subplot has had a lukewarm reception from fans, but that's mainly because it's been given so little room.
On a practical level, Hulk is also easy to keep around because whenever the "Big Guy" is in play, the character is entirely CGI. "The Hulk" - as he usually appears on posters and in trailers - is most recognizable in his transformed state. The role has already been react once, and if Ruffalo ever does decide that he's sick of playing the role, Marvel could quite feasibly recast the character again.
Hulk Stories That Could Be Explored After Avengers 4
There are countless great Hulk comic arcs that many fans would love to see, but we have to keep in mind the fact that Marvel Studios is extremely unlikely to make a Hulk solo movie. The character's Planet Hulk arc was partly incorporated into Thor: Ragnarok, but was necessarily stripped down to the point that the only plot elements included were Hulk hitting a wormhole and crashing on Sakaar, and Hulk taking up a new life as a gladiator.
Just as Hulk was a supporting character in Ragnarok, his future in the MCU after Avengers 4 will most likely consist of ensemble movies and providing back-up in other characters' solo movies. With that in mind, the most obvious place for Hulk to crop up next would be in the planned Black Widow solo movie, as a love interest/backup for Natasha Romanoff - but if the rumors of Black Widow being a prequel movie prove accurate, the continuation of Bruce and Natasha's romance could be foiled again.
Interestingly, Hulk has now joined Thor in straddling the barrier between the cosmic and Earth-based worlds of the MCU. As a scientist, Bruce may well have gotten a taste for interstellar travel, and as such could crop up in cosmic stories like Guardians of the Galaxy 3 or even a sequel to Captain Marvel. Or, assuming all goes smoothly with Disney's acquisition of Fox, Hulk could help to usher in the Fantastic Four whenever they get their first MCU movie. The strength of the MCU's Hulk is that, because he's been established as an ensemble character, he can jump from franchise to franchise without it feeling unnatural - and fans can get a real kick out of say, Bruce hanging out with the Guardians, or Hulk getting into a brawl with The Thing.
The post-Avengers 4 future is looking uncertain right now, but as a character who has been around since the very start of the MCU, Hulk could be just the giant green rage monster we need to usher in the next phase of stories.
- Captain Marvel (2019) release date: Mar 08, 2019