Charlie Demerjian from The Inq claims NVIDIA has taped out a 55nm version of the GT200 GPU. He claims this chip will likely be released in late summer or early fall.
Demerjian claims the yields of NVIDIA GT200 GPU are very bad, says the cards will only be available in limited quantity, complains about the high TDP and says the performance of ATI's RV770 will be comparable to the GeForce GTX 260.
He goes on that AMD's R700 will crush the GeForce GTX 280 in just about every benchmark and says the card will likely cost less but we're not sure what to believe of this as this is the same guy who bashed the G80 to death before it came out and we all know how that turned out. Demerjian is always very negative about NVIDIA and too positive about AMD so please take what he says with a grain of salt.
We'll know more when the NVIDIA GeForce GTX 280 and 260 graphics cards launch in mid-June.