Nvidia 6800XT is nothing more than an eight pipeline 6800 card but in Nvidia's case it will be available for OEMs only. Nvidia will keep its price around $5 below ATI X800GT price and OEMs have to react to such a deal as it means $5 more greenies in their pockets. ATI doesn't have any other choice then to drop the OEM price of X800GT, which is already a very low priced part.
ATI will still have a chance in retail as the X800GT is already available, and will directly fight the 6600GT. Nvidia might have some problems to keep the 6600 GT sales alive at least in the channel, but we suspect that as soon as it happens Nvidia will either lower the price of 6600GT or will just announce a retail version of 6800XT.