The characters first appeared in Marvel's X-Men comic books, as villains under the nefarious Magneto, before later being recruited into The Avengers. The Scarlet Witch, a.k.a. Wanda Maximoff, has the ability to control and manipulate probabilities. Her brother Quicksilver, a.k.a. Pietro Maximoff, has the gift of super-human speed.
The only thing that has been confirmed regarding The Avengers 2 is that Joss Whedon is directing from his own screenplay, which he just recently completed.
Avengers: Age of Ultron comes to theaters May 1st, 2015 and stars Aaron Taylor-Johnson, Scarlett Johansson, Robert Downey Jr., Elizabeth Olsen, Chris Hemsworth, Chris Evans, Cobie Smulders, Jeremy Renner. The film is directed by Joss Whedon.