In the past, we have seen Nikon D800 and Nikon D400 books to show up online. One publisher actually came out and said that their D400 book was a pure speculation. We have discussed this in details before - basically anyone can register a new ISBN number and a book title. The question if this publisher really has some advanced information about Capture NX3 or they are just shooting in the dark. What I find also interesting is the release date of September 1st, 2011 - I already mentioned that Nikon is expecting to have a major product announcement(s) at the end of August.
The last rumor I received was that Nikon Capture NX 3 will be rewritten from scratch and will also include NIK plugins.