We all already noticed in the first Avengers that there's an underlying bit of tension between some of the members (Mainly Captain America and Iron Man). From the overly-rightous, to the ones that are a bit more laid back, you can tell their end-morals are the same, but their ways in obtaining and reaching the greater good, vary.
Vulture had an interview with the brilliant superhero director Joss Whedon, asking him,
"So for Avengers 2, you have a draft done, you start shooting in early 2014. What will be the main conflict this time, now that they've formed a team? Trying to stay a team? Becoming their own worst enemy? Because these are not folks who can pull off making a movie out of a Shakespeare play in twelve days."
Joss Whedon then replied with,
"No, they're not. And actually, that's the middle of the movie, them trying to. It's the Avengers trying to do Measure for Measure, and it doesn't go well. It's very exciting, especially in 3-D. [Laughs] The rest of it, you're right about — it was necessary to build this team, but what happens to them and to the world when they actually exist as a team? How does that work? And I have until we shoot in February to make sure that I'm right."
Great approach for the film in my opinion With so many strong (super) personalities in one room, there's no way anything could continue without a bit of strife in between two or more members. It would be interesting to see what common evil will drive them to work together and put aside their differences once and for all.