GeForce GTX 780
It will pack a Kepler GK110 GPU but with 2496 shader processing units, 208 TMUs and 40 ROPs, on a 320-bit memory interface with GDDR5 memory. It will most likely have a 4GB or 5GB frame buffer and offer similar clock frequencies to the GeForce GTX Titan. Its performance should be over 10% better than the GeForce GTX 680. Expect its power consumption to surpass the 200W mark and its price to be over 500 USD - most likely, 599 USD.
GeForce GTX Titan Ultra
Although not yet confirmed, it's alleged to pack a full Kepler GK110 GPU, which means 2880 Shader Processing Units, 256 TMUs and 48 ROPs, on a 384-bit memory interface with GDDR5 memory.
Its performance, as well as its power consumption, is expected to be practically on level with dual-graphics GeForce GTX 690 and is said to launch with a 999 USD price or more.
GeForce GTX 770 & GeForce GTX 760 Ti
While the GeForce GTX 780 has an almighty Kepler GK110 GPU, the GeForce GTX 770 and the GeForce GTX 760 Ti are stuck with the old Kepler GK104, or at most the more energy efficient Kepler GK204.
In other words, they will be slightly tweaked versions of the GeForce GTX 680 and the GeForce GTX 670.
The GeForce GTX 770 will equip a Full Kepler GK104 GPU with 1536 Shader Processing Units, 128 TMUs and 32 ROPs, on a 256-bit memory interface with GDDR5 memory. Its Central Unit should run a bit faster or at the same speed as the GeForce GTX 680 while its power consumption is expected to remain more or less the same. It's predicted to cost up to 399 USD.
On the other hand, the GeForce GTX 760 Ti will equip a Kepler GK104 GPU with 1344 Shader Processing Units, 112 TMUs and 32 ROPs, on a 256-bit memory interface with GDDR5 memory. Its Central Unit should run a bit faster or at the same speed as the GeForce GTX 670 while its power consumption is expected to be more or less the same. It's predicted to cost up to 299 USD.
___In summary, I think the GeForce GTX Titan Ultra is a bit useless since it's practically identical to the GeForce GTX 690. It hasn't actually been announced though, so it could be the same card.
The GeForce GTX 780 is the next best thing as it will perform much better than the GeForce GTX 770 and thus history will not repeat itself; remember that the GeForce GTX 670 overclocked performed similar or better than the GeForce GTX 680.
The GeForce GTX 770 and the GeForce GTX 760 Ti might be disguised renames but their expected release prices, especially for the latter, are very accessible; they could be worthy purchases.