Looks like the mystery of what the unannounced Star Wars project will be has been solved!  The official Del Ray Star Wars twitter account just tweeted a link to io9 announcing that Joe Schreiber will be turning his horror expertise to focus on Darth Maul.  The book is due out at the end of 2013.

The synopsis of the book, taken again from io9, is as follows:

From the mind of Joe Schreiber, New York Times bestselling author of Star Wars: Death Troopers, comes the delirious follow-up to last year’s Darth Plagueis. In a tale of retribution and survival set before the events of The Phantom Menace, Darth Plagueis and Darth Sidious dispatch Sith apprentice Darth Maul on a secret mission to infiltrate a criminal empire operating from inside Cog Hive Seven-a hidden prison teeming with the galaxy’s most savage criminals. There, he must contend against the scummiest and most villainous in gladiatorial death matches while carrying out his masters’ clandestine commands. Failure is not an option; success will ignite the revenge of the Sith against the Jedi Order.

I’m fairly sure that this never came up in speculation the other week.  Surprise.