There had been rumors some time back that Elizabeth Olsen would be playing Wanda Maximoff, or better known as the Scarlet Witch in the sequel to the third highest grossing movie of all time: "Avengers: Age of Ultron". It still isn't “technically” confirmed who she will be playing, but in an interview with The Wall Street Journal Samuel L. Jackson spilled the beans that Elizabeth Olsen had been cast in the film and that he has no knowledge of who she is playing because he has yet to see a script.
Here is exactly what Jackson had to say:
I know we’re shooting in London, that James Spader is Ultron and going to be the bad guy, and that we added Ms. Olsen, but I don’t know what she’s doing, if she’s on the inside or the outside. I haven’t seen a script.
It’s easy to assume Olsen will be playing the mutant sister to Quicksilver, as most sites are doing, but until there is an official statement or someone says it directly don't believe it until you see it. Although, it's most likely her; who else would she play?