As far as I know there are no dp 1.4's yet. There's another thread about that I've been following also. The general feeling is they will begin appearing in the fall.
As far Jayztwocents 4k doom goes. It's a current game and I already read reviews about the nightmare settings during release. Overall the new engine was well coded and mostly optomized for nvidia(next patch is supposed to add SLI support). It's commendable that a single 1080 is doing well, but there's not much headroom for the games that will come out in the next 2-4 years. I'm pretty sure it won't go much over 80-100fps in 4k either when those monitors come out unless you SLI. At this point SLI is going to need more than the dual x8 current quads are limited to. I can absolutely attest that when I switched to my hex(40 pcie lanes) those 970's gained some frames even when I was still using the same mem(1600mhz), psu, case, cooler, etc. from the z68 board. That being the case in order to stick with these current 1080's you'll need a hex or bigger(way more $$$).
A single faster 1080 will allow a new build with a fast quad, fast mem, for much less money while using 16pcie lanes and leaving some for other things(SSD's etc). Don't get me wrong, I'm a big fan of the EVGA SC cards. Thats what my 780 is and it still mostly rocks 1080p gaming. I also favor the gigabyte g1 series and I'm sure they've got something impressive coming.
I'd say start getting the parts of your next build together and give the gpu market a few more weeks to settle. 6600k, lga1151 z170 mobo, FTW 1080, ddr4 pushing 3333 32gb) pair of 3d nands for a game raid and you'll have a serious and affordable system that will last another 4-8 years.