Sad news indeed. I hope that his health improves at least to the extent of being able to continue playing chess, even if not in tournaments any more. That he is such a fighter may help, though I suspect he will have to take things easy now.
A tribute from Steve Giddins:
http://stevegiddinschessblog.blogspot.co.uk/2012/12/goodbye-viktor.html
I hope Victor the Terrible has many more years left to play chess or at least enjoy being alive and well, but unfortunately time marches on inexorably for all of us. According to another fairly recent news item his old rival and contemporary Spassky is also showing major signs of wear and tear these days. Meanwhile, the oldest GM now alive is Yuri Averbakh,who is 90 and reportedly in good shape for his age.
http://www.chessbase.com/newsdetail.asp?newsid=8716
fburton,
what a game in that link!
Yep, a real slugfest! 
The game is brilliant, and typical for him - Kortchnoi has always been one of my favourite players, because he is so good with black and also so good at fighting back and winning after being at a positional or material disadvantage. The style of play greatly appeals to me:- the lurk-and-pounce - and his style of playing it is inspiring. I wish him all the best for a quick recovery, and that he can continue to enjoy chess for as long as possible.
His French Defense has been inspirational to me, as has Spassky's Queen's Gambit.
A legend is probably retired from Chess.
Started to enjoy chess following the first kaspov- Kortchnoi match
http://www.chessvibes.com/reports/no-more-chess-for-viktor-kortchnoi