Lots of posts on internet forums are speculating what the new Nikon professional DSLR will look like. From trickles of hints and suggestions by someone with claimed “insider” information, the new camera will feature a “revolutionary feature”. It is unlikely just a full frame sensor because Canon had it since November 2002 (the Canon 1Ds 11MP). Some European websites (eg. here) have some more details that look very very interesting. However someone pointed out that the specs are just copied from Tom Hogan’s prediction. For a good history of Nikon D3 rumors, please check out this page by a fellow photography blogger.
For the timing, most speculate late June or early July announcement and around August for initial shipment.