If you haven't seen the post-credit scene (there is a brief description of it) or don't want to be spoiled, abandon thread now...
Brief description of the scene:
Baron Von Strucker
played by Thomas Kretschmann is walking with another man in what looks like a weapons hold/testing barracks. They are discussing the 'volunteers'
and what to do with them (now deceased). Strucker says "bury the bodies".
They walk past Loki's scepter from The Avengers
, (with power eminating from it) Strucker says "They don't know what they had
" (paraphrasing)...they begin discussing the 'volunteers'
again, the ones that survived.
The source of Scarlet Witch's (Wanda Maximoff) and Quicksilver's (Pietro Maximoff) powers, they needed the money (especially if the gypsy backstory is true), and volunteered (could have been forced) to be part of this 'volunteer progam'
by Baron Von Strucker.
Eventually Strucker and the man get to holding cells with both Scarlet Witch (levitating blocks with her hands) and Quicksilver (bouncing around his cell super fast). Strucker says "it's the age of miracles
" (again, paraphrasing). Scene ends with Scarlet Witch making a gesture with her hands, a red smokey looking mist appears and the blocks explode - end scene.
The 'tests' that were done on the Maximoff twins, inferring it's from Loki's scepter power-source, created (mutated?) the Twin's DNA, creating super-powered beings, aka "miracles".
The Avengers: Age of Ultron stars Robert Downey Jr., Chris Evans, Mark Ruffalo, Chris Hemsworth, Scarlett Johansson, Cobie Smulders, Jeremy Renner, Aaron Taylor-Johnson, Elizabeth Olsen, with Paul Bettany, Samuel L. Jackson, and James Spader. The film is set for release on May 1, 2015.