NVIDIA is planning to launch its next high performance single-GPU graphics cards, the GeForce GTX 880 and GTX 870, no later than Q4-2014, in the neighborhood of October and November, according to a SweClockers report. The two will be based on the brand new "GM204" silicon, which most reports suggest, is based on the existing 28 nm silicon fab process. Delays by NVIDIA's principal foundry partner TSMC to implement its next-generation 20 nm process has reportedly forced the company to design a new breed of "Maxwell" based GPUs on the existing 28 nm process. The architecture's good showing with efficiency on the GeForce GTX 750 series probably gave NVIDIA hope. When 20 nm is finally smooth, it wouldn't surprise us if NVIDIA optically shrinks these chips to the new process, like it did to the G92 (from 65 nm to 55 nm). The GM204 chip is rumored to feature 3,200 CUDA cores, 200 TMUs, 32 ROPs, and a 256-bit wide GDDR5 memory interface. It succeeds the company's current workhorse chip, the GK104.
Looking at the specs above anyone with a GTX 780 or better may as well keep their money in their pocket as I don't think these cards are anything special.