NVIDIA's new ForceWare drivers hint the company is planning to release two new graphics cards. The first one is the GeForce 7800 GS and the second one will be a 512MB version of the GeForce 7800 GTX.
The GS will be positioned below the current 7800 GT
Our industry sources claim that NVIDIA is positioning the new GS somewhere below the current 7800GT. Traditionally, NVIDIA’s products that carry the GT suffix tend to be a mid-priced product that carries a significant portion of the top performing variant. GT products are also well received by the community as good value for the money. However, there is a large majority of users out there who don’t play the most recent games frequently and spend most of their computer time doing other things that don’t demand leading-edge graphics performance. We can only assume now that GS products are aimed at a more mainstream audience – and it’s a good thing.
More info at AnandTech. It's not sure when this cards will be available but some sources claim it will be in early November.