To be fair, the endless cycle is entirely in Roland's hands. However, I highly doubt he'll ever give up the chase.
It can serve to get others to read the books if they liked the movies. It can be a bit daunting to enter a bookstore with little clue as to what you might like to read. It's much easier if you already recognize a story and already have some interest in it. Just look how big lore explanations can be based off of movies, tv shows and video games. Star Wars had a ton of lore books and many spawned from video games as well like the Halo books.
Tv shows generally do a good job of condensing the book into a form that is hopefully more entertaining in shorter bursts. IT can be a slog to get through at times, but the tv series was very quick to get the viewer into it. On that note, I worry for the movie as a lot will have to be condensed if it they just go with a single film. Then there's the ending where it was an alien in the book and a spider monster/alien spider in the tv series. Although. not all books are a slog to get through and adventure stories are generally pretty quick to get into unless the author feels like cranking up the autism to 11.
Necroscope would make a fine tv mini series. I think a mini series would be the better option for most books. A tv show can really drag along as seen by the Walking Dead. I understand that the WD is a soap opera, so that a tv series fits it better in that regard. However, a nice condensed mini series would be great.