Doubt it. Coz none of the products except 9600GT will conflict with 8XXX series. 9800 GX2 is definitely a product to counter 3870X2 and ATI's card is already here so why delay your product.
Secondly, mobos based on Nvidia chipsets are due for an urgent refresh. 680i is too old now and 780i is nothing but a ptch up job on earlier technology. Mobos based on Intel's p35 and X38 are real kickass... and by all indications X48 will be a performer too. Even AMD has refreshed their mobo line and it is certainly not a failure like phenom.