If this thing actually does happen, I understand the movie would be 3 parts long, and then have an accompanying tv mini series in between movies?
I would assume the first movie may cover the events of The Gunslinger and Drawing of Three. Im thinking a second movie might cover Wastelands and Wizard and Glass (non prequel part). Maybe then you would have a tv mini series to cover Wizard and Glass. And part III of the movie series would cover the events of Wolves, Song, and DT? I know that part III would end up being long as hell, but I cant see any other way.