Reports Deadline:
The plan is to start with the feature film, and then create a bridge to the second feature with a season of TV episodes. That means the feature cast -- and the big star who'll play [lead character Roland] Deschain -- also has to appear in the TV series before returning to the second film. After that sequel is done, the TV series picks up again, this time focusing on Deschain as a young gunslinger. Those storylines will be informed by a prequel comic book series that King was heavily involved in plotting. The third film would pick up the mature Deschain as he completes his journey. They will benefit from being able to use the same sets cast and crew for the movie and TV, which could help contain costs on what will be a financially ambitious undertaking.
...to say the least! Howard (who intends to direct the entire first season of TV episodes, though I can't imagine NBC intends to commit him to the typical 22-episode order) calls the plan "unprecedented," and I surely couldn't disagree. Who knew that the director of Ed TV had the biggest balls in Hollywood? I'm kind of agog at the multiple ways this could go wrong, but let your fantasy casting proceed apace.