Spoiler Warning: If you don’t want to know what happens in the post-credits scene for Captain America: The Winter Soldier, then stop reading now. Captain America: The Winter Soldier has started screening internationally, and earlier reports of two post-credits scenes have now been confirmed.
Back in February, it was rumored that one of the Captain America: The Winter Soldier after the credits scenes would involve the introduction of Quicksilver and Scarlet Witch. A new report by Belgian pop culture site BrainFreeze.be is confirming that Captain America: The Winter Soldier does mark the big screen debut of these two mutants, except they aren't called mutants in the Marvel Studios Cinematic Universe, since Fox owns the rights to Marvel's mutants. It appears as if they will be referred to as "miracles."
BrainFreeze.be also has the first review of the film, as well as some other spoilers. Here's there translated to English description of both of the post-credits scenes.
Scene 1: After the fall of both S.H.I.E.L.D. and HYDRA we see Baron Von Strucker (Thomas Kretschmann) in his underground lair. Loki’s scepter can be found here, as well as two special prisoners: the “twins”. These are of course Quicksilver (Aaron Taylor-Johnson) and Scarlet Witch (Elizabeth Olsen). Quicksilver is bouncing from one end in his cell to another while Scarlet Witch is stacking some building blocks with her mind. Watching them, Von Strucker announces “The Age of Miracles” is upon us. And with that we learn the new name for mutants in the Marvel movieverse.
Scene 2: The Winter Soldier is visiting the Captain America exhibit in the Smithsonian museum. Here he finds the information on James Buchanan “Bucky” Barnes, his real name. It appears the Winter Soldier now knows who he really was and remembers that Captain America spoke the truth about him.