Comics are not canon...
Orci said himself the Countdown comics were not canon when we all thought they were.
While this is true, the current comic series set in the Abrams timeline is supervised by Bad Robot to make sure they don't do anything planned for the movies. It would be way too sloppy, even for Abrams and his Cohorts to allow Gary Mitchell to be in the very first issue if they were indeed going to use him in the movie.
Or perhaps Urban screwed up and Cumberbatch is actually playing Gary Seven?