[FS]

I don't think he every literally said he'd be retiring, it's more that journalists took his words out of context. He has said though that the Dark Tower is kind of his magnum opus, and when it's done he'll probably be cutting back on his writing more... Plus he's got some illness that's deteriorating his eyesight to -I think- the point of eventual blindness. I can't imagine that'll help his writing career.

I don't really see how a writer could choose to retire, either. Maybe you run out of ideas for a while, but there's no telling what may come in the future.