I kind of think Civil War won't have much to do with its namesake. Rather than a war between Rogers and Stark about hero rights, it will be a disagreement about how political Avengers specifically are in the world. I imagine there to be a civil war in Wakanda. Rogers or Stark want to intervene, because it's the right thing to do, but the other one disagrees, because it sets a dangerous precedent for the militancy of superheroes. It's one thing to stop an invasion, quite another to take sides in a civil war. Rogers and Stark's feud leads them to fighting against one another. Toward the end of the film it's revealed that Man-Ape is working with AIM/some other organization which means Rogers and Stark can defeat the bad guys. It's just a title. Without SHIELD the Avengers are on their own, and the government, no surprise, doesn't like it. And yes, it's Captain America vs. Iron Man with Black Panther guest starring. There's no need for all the Avengers around. Plus, it's a shared universe. It'll follow into other movies thematically. Maybe Hawkeye dies, and Black Widow goes nuts over it, causing her to quit the team, and others have their own reasons.