In his blog Patrick Rothfuss finally says that he'll have the book done by September, and the book should be on the stores on March 1, 2011.

 

http://blog.patrickrothfuss.com/

I can see Rothfuss running into major problems if he doesn't finish by September. He may have done better to say that if he finishes the book by mid-September 2010, it'll be out in March 2011, and if he doesn't, it won't, as Sanderson recently did over TOWERS OF MIDNIGHT (if he finishes by August 15th, it'll be out in November 2010, if he doesn't, it won't).