According to a short report over at Fudzilla.com, it appears that the GTX 780 could launch as early as May 23rd. It is still unclear if it will be a hard launch or is it just an NDA date for reviews to go live, but in any case we'll now for sure in about 20 days from today.
The report also notes that the GTX 770/760 will come on May 30th and it pretty much lines up with what we heard from our sources saying that Nvidia will launch its new graphics cards before the end of this month. In case you missed it earlier, the GTX 780 should be based on the GK110 chip that we already seen in teh GTX Titan graphics cards while the GTX 770 should be based on the GK104-425 one, an improved version of the quite famous 28nm GK104 chip.

The recent rumor from Sweclockers site claims that the price of the new GTX 780 might end up to be well over the earlier suggested US $499.99, making it closer to the launch price of the GTX Titan rather than the GTX 680 back in the day.

Source: Fudzilla.com.