The new Nvidia chipset will make Nvidia graphics cards run faster. This is the dream combination and this is what the future brings. All Hybrid SLI chipsets will work faster with Nvidia boards and if you plug in an ATI graphics card nothing will happen; there won't be any performance increase.
AMD already has marked Nvidia as a hostile and Nvidia is simply returning the favor. It doesn’t take a scientist to figure out that AMD will probably do the same.
AMD’s upcoming Hyper Crossfire (or whatever they end up calling it) will certainly work faster with AMD motherboards powered with ATI graphics better than any other scenario. This will force people to pick Nvidia – Nvidia graphics cards and chipsets from ATI – AMD as this will be the only way to boost performance.