Right now, the Fermi technology is the best that Nvidia is shipping. You can expect to see an ever-growing family of Fermi-based GPUs to be joining the latest GTX 480, GTS 460 and 450 models.
What's beyond Fermi? Nvidia CEO Jen-Hsun Huang today revealed that it'll be "Kepler".
Kepler will be hitting production later this year, with the first GPU products based on it to be going on sale in 2011. Kepler will be made off the 28nm process, and will be focused far more heavily on performance per watt than Fermi is.
Nvidia estimates that Kepler will be three to four times the performance per watt over Fermi, giving us a ballpark of five gigaflops of per watt.
And after Kepler, reaching into 2013, will be "Maxwell", which should bring 16 times the performance in parallel graphics-based computing, as well as the ability to work independent of a CPU. Performance per watt will triple over the previous generation, hopefully hitting 15 gigaflops per watt.