Is it true that Luke Cage has already been cast for this show?
That's an old rumor. There was a speculation a month or two back that J. August Richards's character in the pilot was Cage, but that was disproven.
I just found this article:
It quotes the upcoming Entertainment Weekly
article about Whedon and the show, which contains the following passage:
Then we’re off to the top-secret set of S.H.I.E.L.D., which brings the sprawling Marvel universe to television for the first-ever live-action series in the company’s 74-year history.
What??? Aren't they forgetting the '70s Incredible Hulk
and Amazing Spider-Man
, or Blade: The Series
from 2006? Not to mention the '70s Doctor Strange
and Captain America
pilots, the '90s pilots for Power Pack, Generation X
, and Nick Fury: Agent of SHIELD
, and the '00s Man-Thing