As Anonymous noted below in the comments, Terry Pratchett announced yesterday that he is in the beginning stages of a rare form of Alzheimers. What an odd coincidence to read that on the same day I posted about Discworld. It must have been something in the zeitgeist, as they say. True to his tongue-in-cheek author persona, Pratchett wrote that his statement should be interpreted as he is not dead yet "although someday he will be as will all of us."
For all of his readers -and those of us who want to become his readers - I hope he continues to live a long time and write as much as he can.