I am pretty sure Nvidia are gonna do with 9xx and 10xx what they did with 6xx and 7xx, although with a die shrink to 20nm (or 16nm according to some reports).
GTX 680 and 670 were based on GK104 just like 980 and 970 are based on GM104.
770 was basically an overclocked 680, resulting in 4% more performance.
760 was also an overclocked 670, but with an extra SMX disabled, resulting in 8% less performance.
Exact configuration and clocks can definitely vary this time around, but I expect 1060 performance to be in the same ballpark as 970 and 1070 Performance to be in the same ballpark as 980, with better performance/power ratio, thanks to the die shrink.