I think he's been getting better offers now for bigger budget projects since Hollywood loves adapting other people's stories. If it is a mini-series, we see television actors. If it's a feature film, then we're more likely to see movie stars. I hope they make it a mini-series so they tell the whole story!
On a slightly off topic note, I think I read that Samuel l Jackson had agreed in principle to star in a movie adaptation of one of kings books, but it is still not a done deal. Anyone know of this?
^edit^ It is "cell"