While the G92-based 8800GTS is on track for a December 11th release, and NVIDIA three-way SLI will be released at a similar time, neither will be compatible with the other. It would seem as though NVIDIA is trying to keep three-way SLI an exclusive club for the more expensive offerings from the graphics giant. At this point, only the 8800GTX and 8800Ultra are confirmed to work with three-way SLI, and there is the possibility that the 8800GT will be able to use three-way SLI. While three-way SLI may be possible through software rendering at some later point in time, chances are it will be slow and buggy. The main giveaway for the lack of three-way SLI is the lack of a second SLI bridge connector on the 8800GT.
Source: The Inquirer