I had heard a rumor that 07/07/2007 was the release date of the last book. I think that it is such a big deal overall that everything including the title will be a secret possibly for obvious reasoning not to spoil anything.

I can imagine since it is such a big deal there is so much security surrounding the book and all that it is highly possible that the book could be complete and her camp is kept quiet so as to not give out any spoilers.

I used to work for an author a very popular one (Anne Rice) and you had to keep things underwraps especially when the fandom is so large.

Just my opinion not fact.