NVIDIA's upcoming GeForce 700 series which would be a refresh of its current Kepler 600 series lineup is said to bring 25-30% performance improvement whereas Maxwell has been delayed to 2014.
VR-Zone got these details from their own sources who have suggested that node manufacturing is the main issue behind delays. The launch of the 20nm Maxwell GPU's due to this reason would be pushed to first half of 2014. The Maxwell GPU's would range from the mobile Tegra upto the workstation Tesla boards and would be fused with 64-bit ARM cores known as Project Denver.
As far as current Kepler lineup is concerned, NVIDIA seems to have scrapped of the GK106 core architecture. Previously, the GK106 architecture was presumed to be used by the GTX 650 GPU however new developments suggest that all of 600 series lineup is build up of three core architectures: GK107 for low end, GK104 for performance and the upcoming GK110 for High Performance computing.
The GK110 chip will debut in December with the launch of Tesla K20 featuring 2880 cores (15SMX Units), 384-bit memory interface and a memory of 6-12GB GDDR5. It is unknown though if the same chip would make its way in the GeForce 700 series lineup though a Quadro K6000 6GB based on the GK110 is planned for launch in future. The GeForce 700 series which would be a refresh of this years Kepler lineup would feature the refined GK-114 architecture offering clock frequency improvement which would increase their performance by 25-30% over the current series.
The GeForce 700 series would compete against the HD 8000 Sea Island GPU's from AMD in 2013 while Maxwell would be put against AMD 2014 GPU lineup. Maxwell would be the real game changer in the GPU industry so we can expect lots of new development by 2014.