CITADEL OF THE AUTARCH + 1?Usenet

I was glancing at an ANALOG on the newstands and found a review of PEACE by Gene Wolfe (an excellent little 'novel', by the way, although I'm not sure that 'novel' is the proper term for it given its structure of overlapping and interlaced short stories). I was in a hurry and didn't get a chance to finish the review but it seemed to imply in an aside that CITADEL OF THE AUTARCH will not be the last part of THE BOOK OF THE NEW SUN; can anybody tell me if this is for real and what the name of the last book really is? I like this series so much I actually have all of the volumes published so far, in hardback (and I have two copies of SHADOW OF THE TORTURER).