Though we don't know when we're going to get another Hulk solo movie, Disney is already working on a miniseries for Jennifer Walters a.k.a. She-Hulk. Rumor has it that Mark Ruffalo will be making an appearance as the Hulk, and he just offered us an update on his involvement.
Talking to Variety, Ruffalo explained:
"There's nothing completely at a place where it's a done deal… There's some talk of having Banner/Hulk show up in [the Disney+ series] ‘She–Hulk.' If we come up with something good, that would be really interesting. Right now that's about it. That's all there is on the table."
With She-Hulk's origin tied very closely to Bruce Banner, I would say that they definitely need Ruffalo to make an appearance. He doesn't have to be a mainstay of the show, but I can see him appearing even for just one episode. Though I'm fine if he just appears as Smart Hulk, I think it would be great if we got some kind of flashback of Jen having a talk with her cousin in the form of the human Bruce Banner.
While I don't expect Marvel Studios to follow the comic origin to a tee, I think it's easy enough to have the story that she needed a blood transfusion from the Hulk and that's what gave her powers. Either way, I'd be happy if we got a more creative reason from the writers.
For now, we don't have a release date for She-Hulk, but we could get something by 2022. The first Marvel Disney+ series, The Falcon and the Winter Soldier is aiming for a debut this August.