Whoa, this is huge!
I for one salute Bill. He's been a name at TSR/WotC for about as long as I've been playing the game, and his work is on a number of products that I adore. Bill, good luck in your future endeavors!
Of course, I still can't help but wonder about the details. Like, when is he actually leaving? And is it voluntary on his part? And what, if anything, does this signify for WotC's future?
I know we'll probably never know - and that there's a credible case to be made that we shouldn't know - but I'm still curious.