Still need more than a Titan X though for the frame rates that people are used to. Telling someone that is used to 120Hz, 144Hz, 240Hz and faster gaming that 60Hz or in many instances; sub 60Hz gaming is fine just because it is 4K isn't going to fly. A lot of people don't like to lower the resolution on their monitors also. I can tell you that I have some friends that absolutely refuse to. They are the untapped market that AMD and Nvidia are targeting. These guys spend thousands a year on games alone. Imagine that they could be shown a product that makes them spend some of that cash on hardware.
I think Intel shot themselves; and the rest of the PC industry, in the foot by making CPU upgrades stagnant. There are a lot of people are waiting for programs that task their CPU so that they can buy a whole new machine. As long as they read 5% more performance or no performance at all; just adds DRM, they are never going to upgrade.
I can tell you right now that playing The Division ~42FPS (and that's the highest, most of the time it is much slower than that) on two 980Tis @ 4k isn't all that much fun. It doesn't even use the 3rd GPU I have so I had to disable it.
I see all these new PC games marketed as "4k compatible" yet they don't even have a SLI profile or DX12 mpgu support.