Avengers: Age of Ultron director Joss Whedon teased in a new interview that the film will be darker and more sci-fi-flavored.
"The model I'm always trying to build from is The Godfather: Part II, where a ton has happened in between and it's a very different movie, but you don't need any information," Whedon told Total Film in the issue on stands now. "You're in the vernacular of the first movie and you're ready to just pick up in this new place. It's got a sci-fi element to it that's stronger than the other film. And it's a little bit darker. Getting the team together was so rousing, but keeping the team together is a completely different problem."
The first film, of course, dealt quite a bit with the conflict between the characters as they tried to put the team together. To that end, the "keeping the team together" comment promises more of the same -- so at least there should be some tonal stability there, even if the rest of the film is fairly different.
Avengers: Age of Ultron is due in theaters on May 1, 2015.