Can you return the 1070? That's a lot of money to be wasting if you cant, you really should have bought the 1080 in the first place if your goal was 4k gaming. A 1070 will do 4k in many games but it will require that you drop the settings by quite a bit in some games to achieve 60fps or close to it.
Do you want a 4k tv to use as a tv and monitor? If you plan to leave it hooked up top your pc I would not recommend a 4k HDTV, many have horribly bad response times and input lag. I would personally recommend a high refresh rate 1440p monitor for gaming over any 4k 60hz monitor or TV, pixels aren't everything and it will work well with your 1070. If your heart is set on 4k for some reason, I would look at a monitor with decent reviews over any tv if it's primary use is going to be for gaming.