sbojmir

dont forget that the main cause in the difference of performance is how the PCB is designed... also Nvidia Green light will help suppress that, but in my opinion i would much rather Nvidia make the 780 a 4gb model of the Titan and then drop performance down little by little for each teir of card. im getting bored of them holding back on there hardware when they know they can like go "<.< thats so slow look at this" and a nuke goes of... if they expect people to keep pooring money at 15-30% increase in performance each generation then they are going to loose sells.
i know for a fact that the people who work at Intel and Nvidia are able to make the current generation look like athlons CPU's with onboard graphics, but there companies limiting outflow really suppresses there ability to actualy do allot better than they should be. im sure if they go  "fuck it" on the next generation of hardware and dont go half ass with anything then wait a few years later and do the same again rather than drip feed everyone with a more or less copied and pasted form of what they have already done it would be soo much better.

expect it around around e3 or just after e3

There have been no leaks so far and just like any leaks, it's to be taken with a grain of salt just like with the Titan. The leaked Titan result showed equal or a bit higher than the 690 but when it was released, it was only about 80% of 690.

After 2-3 weeks new gen 700 series is comming.Why don't you buy 770 or 780 and you will save a lot of money and you can play all the games at max settings for quite long time ;)

I would definitely leave the 680 out of this one if you're going for high resolutions. The only 3 cards I'd go for are the 690, Titan and 7990 at 1440p/1600p. If you're running on a 1080p monitor which I hope you aren't, especially with this kind of horsepower you're going to be getting, I'd say any one of these three cards by themselves would be able to run Crysis 3 maxed out no problem on a single 1080p monitor no problem. Dual 680s will do better compared to the Titan in this resolution though.
Here's Linus's benchmark on the Titan
If you're going to 1600p I'd go for the Titan seeing as the Titan trumphs the ARES II which is essentially a 7990.