According to a source they got a look at the post credit scene for Captain America 2 :The winter solider. The after credit scene is suppose to feature 2 characters that have an upcoming part in the Avengers 2 Age of Ultron storyline.

They’re calling them “The Twins”, the brother-sister team of Quicksilver and the Scarlet Witch, and they don’t look like any Marvel heroes we’ve met to date. Having seen them, I am really sad for Fox and the X-Men…

It would seem that Quicksilver & Scarlet witch will not only play a part in the upcoming X-Men: Days of Future Past but also Avengers 2. Is this a merging of the genres? How will Marvel be able to explain the characters Powers without calling them mutants. One of the main themes of Marvels films and the TV show agents of shield is that the characters get their powers from magical sources, accidents ect. I.E. Avengers as opposed to X-Men (Mutants).

Captain America 2 post credit scene Revealed