In a recent interview it sounds as if Alay Taylor just confirmed a Doctor Strange movie for Marvel Studios Phase 3 plans.
When asked which characters he would like to tackle after Thor 2, Alan Taylor lets it be known he likes the weirder Marvel characters with mention they are doing Ant-Man, Guardians of the Galaxy and "then Doctor Strange."
Here's the quote from the UK's Telegraph:
“I do like the weirder ones,” he says. “What’s cool about them is they can now start exploring the weirder ones because they had so much success with the mainstream ones. So Ant Man is coming along, Guardians of the Galaxy, you know a raccoon is one of the main characters and that’s nuts. And then Doctor Strange. They’ve got lots of places to go.”
Some fans even think Doctor Strange is involved with the return of Agent Coulson as Coulson keeps referring to a "magical place" he was sent to on Marvel's Agents of S.H.I.E.L.D.
Kevin Feige most recently also confirmed the supernatural side of Marvel is in development though didn't make specific mention of Doctor Strange.
Update: Feige confirms Doctor Strange.