Doctor Strange is at the top of the list when it comes to new leading characters most likely to be introduced in Phase Three of the Marvel Cinematic Universe as another member of The Avengers.
While Guardians of the Galaxy will blow open the cosmic side of Marvel, Doctor Strange can open the mystical and magical. Strange not only has super powers but is a neurosurgeon - perhaps in the live-action adaptation his medical (and possibly magical) backgrounds could be behind Coulson's miraculous recovery.
Do Nick Fury and S.H.I.E.L.D. already know about Strange?
Verdict: Strange is definitely coming but his being behind the survival of the main character of this ABC TV is too extreme and doesn't fit.