I sure think near enough all of his work will be adapted, because to a degree that's already the case. But some adapatations seem doomed like The Talisman - and it's hard to say why they just can't do it. We got The Dark Tower, it was not what most wanted, but the film is there. But The Talisman, despite many people having worked on it, over and over gets shut down. The last time we heard it was gonna be produced by Frank Marshall, but it's gone quiet again.
And it's gone quiet on other projects, like The Long Walk too (even with Darabont attached, who you'd think they would let go ahead with ANY King-book). Some just fail several times and then it becomes hard to believe they will ever see the light. And these are also older books, so there may be a feeling with producers to rather go with the more recent ones first that are still more in the general memory, or to do remakes of films that are already well-known.
The Jaunt was another one that was announced, and sounded like an interesting one to do. And that's gone quiet too. And you just seldom hear why.