This morning NVIDIA had unveiled the GeForce GTX 200 series
and already NVIDIA's Aaron Plattner has committed support for these cards to the open-source xf86-video-nv
driver. This support just involved adding in two new PCI IDs for the GeForce GTX 260 and GTX 280. No other work was needed, since of course this driver is limited to mode-setting and 2D acceleration. Though if you've just shelled out $399 or $649 on a graphics card, changes are you will want to stay clear of this obfuscated driver. If you want to check out this driver, you'll need to obtain it from git on FreeDesktop.org
NVIDIA hss yet to publish a new binary-only driver for the GeForce GTX 260/280 to take full benefit of these newest cards, but an update would be expected soon.