There are a series of informations or rumors rolling in about a possible double announcement in October. Both Canon and Nikon would be readying themselves for major announcements targeting the highest end of the market. It would be a Canon EOS 1D Mark IV and a Nikon D3s (or D3x).
But this is still to be confirmed.
Sources: Shots.fr, Nikon Rumors.
Update: The D3s is now confirmed for October 15th, by another source (via RP).