Yes, he has, such sad news. It isn't on his site yet, that's probably the last thing they are thinking about, but it's on Eclectic Horseman.
Everyone is putting thoughts on this thread. (Glad someone here knows who I'm talking about). http://www.eclectic-horseman.com/horsemanship/showthread.php?p=8416#post8416
I saw him at the Equine Ethology conference, did you? He had so much to teach people who some might have thought were already at "the top". The comments on EH are nice to read.
Such sad news, I saw his clinic some years ago, I have never seen anyone achieve so much with a horse by appearing to do so little. An awesome, awesome man.
We are lucky that he kept on sharing his knowledge right up to the end. There are some great horsemen around who are strongly influenced by him, so his work lives on.