In a recent interview with BuzzFeed, Marvel Studios President Kevin Feige has confirmed that the Avengers line-up is definitely set for some changes. He explained,
“The Avengers films, ideally, in the grand plan are always big, giant linchpins. It’s like as it was in publishing, when each of the characters would go on their own adventures and then occasionally team up for a big, 12-issue mega-event. Then they would go back into their own comics, and be changed from whatever that event was.
“I envision the same thing occurring after this movie, because the roster is altered by the finale of this film.”
The “this film” he is referring to is Avengers: Age of Ultron. As we saw in the trailer earlier things get incredibly intense between the Avengers team, and that is going to carry on into the Civil War storyline that we will see in Captain America 3.