Nikon Rumours seems to have spotted the right information: Some Nikon dude working on the web site pages for a new camera named Nikon D3x. It has been showing images during half an hour. Not much, but a serious confirmation of the name of the new pro camera at Nikon: Nikon D3x.
Here are the photos:
But nobody has precise features to describe (apart from the obvious 35mm Full Frame sensor).
Most probable publication date for the announcement: 1st or 2nd of December 2008.