In the first Space Jam, mega-star Michael Jordan was also joined by Charles Barkley, Larry Bird, Shawn Bradley, Larry Johnson, Patrick Ewing and Muggsy Bogues.
James is an executive producer on the film who certainly has pull to have these discussions with other basketball names.
The addition of other talent from the basketball world would certainly buff up interest in the movie from the fandom and allow some other players to be a part of this movie event.