The next member of Nvidia's Maxwell family could be just around the corner. Sources cited by Videocardz suggest the GeForce GTX 880 will be announced in mid-September, with availability to follow at the end of the month. The card will reportedly have a GM204 GPU with a 256-bit memory interface. Videocardz doesn't have a firm sense of clock speeds or unit counts, but 4GB of GDDR5 memory is expected to be the default configuration. Some card makers are said to be prepping 8GB versions, and you can probably bank on a range of hot-clocked variants.
There's some evidence that a GM204-based card is near, too. According to Videocardz, a "PG401" reference card "recently visited a certification office." The associated document lists a "GM204 256BIT" graphics card specifically. It's also dated June 6, which doesn't sound particularly recent to me. Hmmm.
In any case, there's more. Liu Mengzong, the marketing director for Gigabyte China, told Expreview that a "GTX 800 series flagship product" is coming in September. The quoted words are Expreview's, not Mengzong's, and they've been through Google's translation engine. Even so, they're hard to misinterpret.
These latest tidbits complement earlier rumors and evidence related to a GTX 880 based on Nvidia's latest Maxwell architecture. It sure seems like this thing exists, and if the latest information is correct, we won't have to wait too long for official confirmation.