Details in regards to the role Rachel McAdams is playing in the Doctor Strange movie have become known.
EW.com has an article featuring comments from Marvel Studios president and producer Kevin Feige, executive producer Stephen Broussard, and Benedict Cumberbatch revealing Rachel McAdams is playing a fellow surgeon to Cumberbatch's Stephen Strange; however, the specific name of McAdams' character is not revealed:
Rachel McAdams plays a fellow surgeon that has a history with Strange and is his sort of lynchpin to his old life, once he steps into he role of a sorcerer. She is someone he connects with at the beginning, and reconnects with, and helps anchor his humanity.
Rachel McAdams is sort of [Doctor Strange’s] contemporary in the modern-day New York world, before and after he goes on this crazy journey. So, she sees him before, she sees him after. She’s kind of this audience point of view.
I’m not sure if I’m allowed to say what the interest is. But if I hit on her more than the Ancient One, put it like that.”
It's also been confirmed that Tilda Swinton is playing the Ancient One, with Mads Mikkelsen said to be the big bad of the movie,
"Doctor Strange" has a November 4, 2016 release directed by Scott Derrickson.
“Doctor Strange” follows the story of neurosurgeon Doctor Stephen Strange who, after a horrific car accident, discovers the hidden world of magic and alternate dimensions.
“Doctor Strange” is the latest film in Phase 3 of the Marvel Cinematic Universe. Phase 3’s goal—over the course of four years and nine films—is to introduce audiences to new heroes and continue the adventures of fan favorites.