For an example, take the latest Deus Ex: http://www.techspot.com/review/1235-deus-ex-mankind-divided-.... It is also a good example for the next statement: The heaviest games don't even get 60 FPS on 1440p, on Ultra the average with a GTX 1080 is 43. 4K is at 24, basically unplayable. Even if you were to use SLI, which is by now pretty much agreed upon to be more a hassle than worth it, it wouldn't be at 60 FPS. And that disregards that 2x1080 are/were 200% the price of a single GTX 1080 Ti, and won't be close to getting 200% the performance.
You can see that as you want, but I can pretty much guarantee that gamers, at least the segment of gamers that would even consider investing hat much into a gpu, will absolutely sprint to get a GTX 1080 Ti, if the performance increase is real. They need it for VR + 4K, or at the very least believe so.
The best part is, in two years (or four) when you buy a better card, all the titles that are currently new will tend to look about as good as 2-year-old titles look now. ;)
I've crunched the numbers and the 1080TI will essentially offer the 980 SLI performance at its best - and that's before the extra RAM and Pascal features come into play - as well as the reduced heat levels etc.
So count me in, especially when Vega comes out and presses the prices further south. (Alas my monitor uses GSync, so that won't be an option for me.)
FWIW I'd like to mention that the 34" screen is completely brilliant for programming (Visual Studio), which is what I use the setup for most of the time.
You can't get any games above like 30 fps on 4K monitors even without maxing out graphics options on a $350 card today. Add multiple monitors... slows to a crawl. You can hear the fans working to keep up with non-gaming tasks...
While I do feel like noticeable CPU performance enhancements have mostly plateaued, I think we are 4-5 years away from affordable and good 4K graphics cards. The choices on the market at present aren't all that amazing. You either pay a lot for meh, or a fortune for acceptable.
Nothing on the market today is like, "OMG it handles anything we throw at it without breaking a sweat..." And that's fine... it's usually 2-3 years after a game comes out that I can run it at max settings.
4k@60 gaming on a single card is an excellent goal. I'm running a single 1080 for this purpose at the moment and on many games it struggles and I have to reduce options significantly.
The 1080Ti should be performant enough to run 4k@60FPS on most games on a single card. The 1080 was close, running ~45-50 FPS, but this should push it over that edge.
Then there are the people who want 4k@144 and stuff who'll be running 2 of these in no time and still not getting the numbers they want...
Hopefully within a few iterations 4k@60 will get down to an affordable level. I just really want to go back to buying $300-500 cards instead of $1k cards and this means we're on the way.
Second, it's all about pixel count. While 4k is still miles ahead of even the 3440x1440 ultra-wide resolution, that resolution represents nearly as big a jump in pixel count as the jump from 1080p to 1440p.
The goal is 4k at a minimum of 60fps. Consistent 100 hz or even 144hz on an ultra-wide 3440x1440 monitor represents a solid step in that direction.