A number of fan sites found a deep-linked image of LEGO Star Wars Super Star Destroyer Executor as seen here. Multiple figures are included, but there's no actual listing, and the deep-linked image hosted on LEGO.com has since been taken down. But there it is!
The set has not been confirmed yet, but obviously an appearance on LEGO.com is pretty dang close. Minifigures included are IG-88, Bossk, Dengar, Darth Vader, and, if I squint right, potentially Admiral Piett. A tiny standard Star Destroyer and a pieces to help display this clearly massive set are also included.
Were I a betting man, I'd guess availability in or about July 2011-- and I expect it will be exclusive to LEGO.com or shared with a retail partner and not a mainline item.