I could imagine that two 970's should be able to handle it. But i think you will be under 60fps, not an expert but i just dabbled a bit..
https://www.youtube.com/watch?v=anhwXkTN8Nc
The gpu market has yet to have a true answer to 4k unless you got a beefy card or a truly amazing sli setup or triple sli. Like i said take what i say with a grain of salt, i want go to 4k too once the market has plenty of 4k displays, that rog is still my choice since you can't run 4k off one card as of yet.