A lot of things changed for a lot of our favorite heroes in Avengers: Endgame. Some heroes died, others exited the main stage in other ways. We knew the future of the Marvel Cinematic Universe was going to be something quite different, and now we know many of the ways those changes will manifest. However, one often overlooked Avengers is Bruce Banner/The Incredible Hulk, and the events of Endgame have also changed his life in a major way.
The Hulk is the one who risks his life by being the one to use the Infinity Stones to return life to the universe. The act very nearly kills him, and leaves him with one severely damaged arm. Endgame directors the Russo brothers have now confirmed that Hulk won't simply heal from this damage, instead, it's permanent damage that Bruce Banner will have to deal with going forward. According to Joe Russo...
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.
An Incredible Hulk who has lost a lot of strength is certainly a very different Incredible Hulk. Mark Ruffalo's character is one who we expect will continue forward in the MCU, but this change will go with him.
Joe Russo admits to ComicBook.com there's really no such thing as truly "permanent" when it comes to this sort of thing in Marvel movies. In a world of magic and super advanced science, the possibility for Hulk being healed is certainly there, but the point is that Hulk will need to be actively healed in some way for this damage to go away, he's not simply going to heal if he puts some ointment on it and wraps it in a cast. Also, as Joe Russo puts it, for him the damage is permenant, because it's somebody else's job to figure out what happens next...
Maybe someone helps him repair that. Maybe someone gives him a new arm. I have no idea where that character goes from here. The nice thing is we didn’t have to pay attention to where it goes after this, we just try to tell a satisfying ending.
Joe Russo draws something of a parallel between Hulk's arm an Natasha Romanov. Both are gone, seemingly forever. One has left physical scars, the other has certainly done some emotional damage. While the relationship between Bruce Banner and Black Widow was never fully explored on screen, it was made clear that there were feelings there, and Bruce will now have to deal with them without her.
Of course, how the future of the MCU will deal with Hulk is a significant question on its own. Hulk has only been a supporting players in the various Avengers movies and Thor: Ragnarok since Mark Ruffalo took on the role. The only Hulk solo movie in the franchise was the second MCU movie made, and there has been no indication that a Ruffalo-led Hulk movie is even being considered. Marvel Studios shares the film right to the character with Universal, so making a Hulk focused movie is a bit tougher than it is with other characters.
Since the future of Avengers movies is also a big question mark, we have basically no idea wen we'll see Hulk again, or how this change in the character could manifest if and when we do.
Hopefully, we will see more of Mark Ruffalo and the Incredible Hulk very soon. Hopefully Marvel will give us a hint when that might be soon, since the entire future of the MCU is a big black box right now