Captain America 3 has an official synopsis:
“Following the events of Age of Ultron, the collective governments of the world pass an act designed to regulate all superhuman activity. This polarizes opinion amongst the Avengers, causing two factions to side with Iron Man or Captain America, which causes an epic battle between former allies.”
It sounds like Age of Ultron will be even more destructive than we previously expected. The events of Age of Ultron will evidently replace the Stamford explosion as the initiating spark of the war.
It’s interesting that the synopsis says that the Avengers will be polarized, not heroes in general. Although Black Widow, Hawkeye, Cap, and Iron Man have all been confirmed for the film, there are still numerous unconfirmed Avengers. The Rumor-Mill has hinted at reasons why the list has been shortened. Of course, if these turn out to be true, this should be counted as a spoiler alert. If you don’t want to hear the theories, scroll down to the Red Text.
First off, there has been the rumor for almost a year that Hulk will find himself space-bound at the end of Avengers 2. In similar to Captain America 1’s ending, Bruce finds himself on a plane heading out of the atmosphere (introduced again in Guardians 2, presumably).
There has been a lot of talk about Thor’s roll. It’s possible (and has been rumored) that he will abandon the Avengers due to the questionable actions of his teammates (especially Iron Man).
There has been rumors that Scarlet Witch will be in the film, but not Quicksilver. Such rumors are synchronized with the rumros claiming that Quicksilver will die during Age of Ultron. Although the exact contract length for Aaron Taylor-Johnson has not been revealed, he has said it was a multiple picture deal, so this seems unlikely.
There are surprisingly no rumors regarding the Vision. So we’ll just have to see what comes from that.
Begin reading again, spoiler-phobics.
Truthfully, the synopsis itself doesn’t tell us much at all. It’s the storyline we knew from the title, but it’s good to see it in writing. Filming begins in about two weeks. Hopefully we will get some interesting set pictures (as we do for most movies) that will shed some light on the film. For now, only time will tell.