"His next book, The Wind in the Keyhole, is a Dark Tower novel, part of a sequence that King plotted and began when he was little more than a teenager himself. The sequence took him years to finish, and he only finished spurred on my his assistants, Marsha and Julie, who were tired of fielding fan letters asking when the story would be completed."
So the re-write being referred to is how many stories like TWTTK might still be undiscovered.
So, yeah. If you actually read the whole article, there's not much truth to the idea of a rewrite.