It sounds like Mark Ruffalo knows what he wants to happen next for Bruce Banner/Hulk. Here's what he recently said on The Late Show with Stephen Colbert:
I don't know [about Hulk coming back]. I do know that I did give Kevin Feige the Blockbuster Award at the Hollywood Film Awards the other day, to a smattering of applause. And he did say 'Hey, do you think there's any more story left here?' And I said 'I could probably come up with a few more storylines.' And he said 'Well, maybe you should come in and we'll have a talk.' You heard it here.
This is not the first time Mark Ruffalo has mentioned one of his little chats with Kevin Feige -- and I picture them eating some shawarma together, or maybe taking selfies with fans in diners. A couple of years ago, when Thor: Raganok first came out, Ruffalo told CinemaBlend that Feige had pulled him aside and asked him what he would want them to do if they could do a standalone Hulk movie...
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.
It sounds like Mark Ruffalo's input was factored into the arc Hulk got from Thor: Ragnarok to Avengers: Infinity War and Avengers: Endgame. So now Ruffalo and Kevin Feige are due for another meeting to plan the next arc. That's what it sounds like, anyway. Feige did recently confirm that She-Hulk and two other new Marvel heroes will be coming to the big screen in MCU movies after their Disney+ shows debut. I wouldn't be shocked if She-Hulk was joined by her cousin on screen.
Avengers: Endgame did set up Hulk for some potentially interesting storylines. The Snap nearly killed Hulk, and the Russo Brothers confirmed it left him with permanent damage:
He’s lost an arm. He lost Natasha. That’s not coming back. He’s damaged himself. I don’t know. It’s interesting. That’s permanent damage, the same way that it was permanent damage with Thanos. It’s irreversible damage. His arm, if you noticed, is a lot skinnier. It’s blackened. So, he loses a lot of strength there.
The Hulk lost some strength and has heartbreak from losing Black Widow, but he must also be hurting from losing Bruce Banner's fellow Science Bro Tony Stark.
Do you see a place for Hulk in that lineup as a key supporting player, like he was in Thor: Ragnarok and Avengers: Endgame? Mark Ruffalo said he was excited about Spider-Man's MCU return, and I could see Bruce Banner as a potential new mentor for Peter Parker after the loss of Tony Stark.