I also doubt that Rockstar would let them. They're incredibly savvy when it comes to the GTA franchise, in terms of marketing and appeal, as the leap to more celebrity actors and a genuine soundtrack for Vice City shows.
Even if this movie gets off the starting block, it won't be with Uwe Boll at the helm. GTA is a Triple A-List franchise, and he's too busy hoovering up D-list fare like Bloodrayne and Alone In The Dark to even register on the radar for this.