Why buy 6700K now when 7700K is 2 months away and will potentially overclock to 5-5.1Ghz on air?!
The call for 6800K is even worse since Intel is releasing X299/LGA2066 next year. This new workstation platform will carry Intel's Skylake-X, Kaby Lake-X and Cannonlake-X, which means the Ice Lake-X on a new workstation socket probably won't launch until 2020!
A case can still be made for a fire-sale Z170+6700K before 7700K+Z270 launch. Either way, X99 and 6800K sits nowhere for someone intending to build a new rig to keep for 5 years. For games, 7700K will smash 6800K.