That's because of the success of IT of course. But it's a lot of remakes and adaptations of his latest works. There are still a lot in between that no one ever seem to touch: Insomnia, Rose Madder, The Regulators, The Girl Who Loved Tom Gordon, Black House, From a Buick 8, Blaze, Duma Key, Joyland (although Tom Gordon and Buick were tried at some point). And there are still a huge amount of short stories never done, and some novellas.
I get the idea they either want to do a remake of something well known (like IT, or Tommyknockers - which despite not being one of his best, was still one of his best selling) or do a recent book whille it's still fresh from the bestseller lists.