"Joss [Whedon] is in his full height of his powers. This movie is much more sprawling and epic than the first one. They're really in an existential, dire crisis. It has a darker quality. The Avengers are really struggling with their own shortcomings and the dissolution of S.H.I.E.L.D. and where they go and who they are in the world. There's a lot of negativity towards them."
The actor also teased that his character Bruce Banner is getting to a point where he has to start accepting his Hulk alter-ego.
"I think they set it up nicely now that Banner's turning 46 years old, and there comes a point where it's like 'how much more running can I do for myself?' Whatever you hate about yourself or you don't like, when you get to be 46 years old, you start to say 'okay, no.' Obviously, you can never really get away from yourself, so you start to live with some of the things you think are so bad. And maybe they're not that bad. Maybe those things are what you need to do whatever you were never able to accomplish."
He teased that in Avengers: Age of Ultron and beyond, possibly with a stand-alone Hulk movie, Banner and Hulk each have to come to terms with one another.
"I think that's the ticket forward for Banner, to start to figure out where we go with him, to keep that story interesting. I think there's a whole relationship with Banner and Hulk that needs to be discovered. There's a very cool thing happening: Hulk is as afraid of Banner as Banner is afraid of Hulk. It's in the comics. But because you haven't really been able to get inside of Hulk's head, because the [cinematic] technology wasn't available to make it nuanced enough to do that, and now it is. So now I think there's a way to do it. Both of these guys are obviously the same guy, and they have got to come to peace somehow with each other. And I think that this confrontation is building along the lines of this film."
The actor also teased that future Hulk movies may deal with this confrontation between Bruce Banner and his Hulk alter-ego.
"He's terrified of him. What makes Hulk afraid? It's himself. It's a version of himself that's weak. It's a version of himself that's vulnerable. It's a child inside of him. It's very interesting, and I'm stumbling on this. And I don't know if this is where the next version will go. But if it is in the cards that we're doing the next version of this, I see some fertile ground there. I've been mulling this over now for a few years. And I haven't pushed for it because I honestly didn't know what hadn't been done. And this time, there's an interesting confrontation on the horizon between these two. It's existence. They're fighting over existence, you know?"
Avengers: Age of Ultron comes to theaters May 1st, 2015 and stars Aaron Taylor-Johnson, Scarlett Johansson, Robert Downey Jr., Elizabeth Olsen, Chris Hemsworth, Chris Evans, Cobie Smulders, Jeremy Renner. The film is directed by Joss Whedon.