User blog comment:Spencerz/X-Men: First Class sequel/@comment-4416729-20120602144904/@comment-3317214-20120606092129

Nope. Marvel Studios and Fox both own parts of Scarlet Witch and Quicksilver. Basically, both companies can use them, but if Fox wants to use them, they can't become Avengers. They'd pretty much stay aligned with Magneto and have their origins told, etc. But if Marvel wants to use them, they can't mention mutants, Magneto, or pretty much any of their backstory. So, because that's a pretty heavy part of who they are, I doubt we'd be seeing either of them in a Marvel film any time soon. We might have a small mention, or a hint that they exist, but I can't see them showing up in time for the Avengers 2 anyway...