SemiAccurate reports that Nvidia is working on two GPUs based on the GK114 and GK114-GX. As of yet, it's unknown whether these chips will both be developed fully, or whether a single chip will be used for both mid-range and high-end graphics cards, as the manufacturer has done with its current Kepler models. The GK104 chip will also be revised, updating the architecture with the latest technologies.
If the sources are correct, there's not that much to the upcoming generation of graphics cards. Who takes the crown when it comes to price/performance ratio remains to be seen, though. Both AMD and Nvidia's upcoming models are roughly 15% faster than the current generation. Both parties are using the same production processes and are therefore bumping into the same limitations. Although the performance doesn't change that much, the new cards should be a lot more efficient than current models, resulting in an improved performance/watt ratio.
As it stands, Nvidia's GTX 700 series is slated for release in March of 2013. Given the fact that the production process is the limiting factor though, it may take several more months for the cards to become readily available.
The performance-per-watt is improved significantly with the new Maxwell GPUs.