Rumor site FUD Zilla claims NVIDIA plans to introduce the GeForce GTX 780 on May 23rd at 6:00 AM PDT, while the GTX 770 should follow exactly one week later. The site says the cards will be a bit faster than the GTX 680 and GTX 670, but not a lot.
The runner up card is dubbed the Geforce GTX770 and it comes on 30rd May 6:00 AM PDT. These dates are valid for the top tier one customers. GTX 780 is based on the GK110 chip that ended up in Titan cards while GTX 770 is based on GK104 425 an improved original GK104 28nm chip.