I find it interesting that they can use Quicksilver and Scarlett Witch. I thought there was still licensing stupidity where Fox still has rights to all things mutants, even though Disney owns Marvel.
From what I understand, Fox owns the rights to "Quicksilver" and "Scarlett Witch" and Marvel owns "Wanda Maximoff" and "Pietro Maximoff." At the very least, Marvel can't use the characters' paternal ancestry or call them "mutants." It all ties into their numerous appearances in both X-Men and Avengers books, and that they're almost different characters based on their interactions with the respective teams. Whatever the case is, I'm pretty sure that they're going to be major players in Avengers 2, and I'd guess that Quicksilver is going to be not much more than a throw-in for Days of Future Past; basically an appearance to stake a claim. I'll be surprised if he's a major character.