Joaquin Phoenix originally accepted the role but then stepped away
I saw that. He had too many projects so he couldn't commit to Dr. Strange (partially because the Strange character may appear in a future Avengers film as well). On that note, Cumberbatch must be thinking "Who needs sleep?"
wonder if we'll see any "Falcon" in the next movie? Nice addition in the most recent Captain America movie.
I don't know how much of a spoiler this is at this point, but skip if you don't want a mix of speculation and actual events...
*******SPOILER*********
Falcon has taken over as Captain America from Steve Rogers in the comics. This appears to be a permanent change, not a "Death of Captain America--until next year" gimmick. Cap is now old and no longer under the effects of the Super Soldier serum, so he now works behind the scenes while the person who was Falcon now dons the Star-Spangled Avenger's costume.
There is speculation that eventually this is going to happen in the movies too. At the very least, I'd be shocked if Falcon didn't play an increasingly larger role in the Avengers and Cap movies.
*******END SPOILER******