Other actors like D.B. Woodside and Lance Gross have also made it clear that they’re interested in the part.
It’s entirely possible that the Green Lantern casting has already been done, and we just don’t know it yet.
Tyrese Gibson has been lobbying for the role for quite awhile now, and has reportedly met with Warner Bros. to discuss it already.
Sterling K. Brown would be far from a bad choice for the role of John Stewart, however, the actor is going to have some stiff competition for the part.