I cannot help with rumors and personally I don´t know any authors except wisnewski/scheerer.
I prefer to check the websites of everyman, gambit, new in chess, chess-stars, batsford, olms, kania, sahovski etc.
Another source is checking amazon for chess books and sorting for publication date.

I´m looking forward to

The Black Lion by van Rekom & Janssen, New in Chess, dec 08?

Play 1b3!: the Nimzo-Larsen attack by Odessky, New in Chess, dec 08?

Mastering the chess openings vol.3 by Watson, Gambit, oct 08?

Encyclopedia of Chess Openings vol. E 4th ed., Sahovski Informant, oct 08?

tracke 

Any rumors about soon to be published books? Which books are you awaiting? Seems Kasparovs book will be out soon. 
I personnaly wait for the Anti-Kingsindian book by Dembo and the follow up of the Khalifman-series,although there is no Information at the chess-stars website.
Also I saw that Ivan Sokolov is writing a book on pawn structures...