With Iron Man 3, the opening salvo in Marvel Studio's Phase 2, pretty much out of the way, attention is turning to the other movies that the studio has coming our way, with the big one being, of course, The Avengers 2. Speaking at the Iron Man 3 premiere, Joss Whedon teased that he was working on the script and has included, as he put it, "my two favorite characters from the comic book, a brother-sister act". For fans of The Avengers comic, this can mean only two people: super fast Quicksilver and probability altering The Scarlet Witch. The son and daughter of mutant Magneto, their rights issue is a strange one. Since they they play a big part in both X-Men and Avengers lore, they are owned both by Marvel Studios and Fox, who have the rights to all things X-Men. So both studios can use them, with the proviso being if Marvel uses them they can't mention them being mutants or their relationship to Magneto, and if Fox uses them they can't mention anything to do with The Avengers. Though it seems likely if one studio uses them first, the other wouldn't want to touch them.
Their involvement in Whedon's draft of the script was slightly illuminated by producer Kevin Feige, who when pushed by Entertainment Weekly on whether they will appear in the movie, said, "I am not confirming or denying. The draft could change six months from now." So Whedon has written roles for them in The Avengers 2, and despite Feige saying the draft could change, it might be a safe bet to assume they'll appear. The movie is due out in 2015, and with a movie of this size and scale, I expect pre-production to be at a point where the characters have been locked in.
Their involvement in Whedon's draft of the script was slightly illuminated by producer Kevin Feige, who when pushed by Entertainment Weekly on whether they will appear in the movie, said, "I am not confirming or denying. The draft could change six months from now." So Whedon has written roles for them in The Avengers 2, and despite Feige saying the draft could change, it might be a safe bet to assume they'll appear. The movie is due out in 2015, and with a movie of this size and scale, I expect pre-production to be at a point where the characters have been locked in.