A raw estimate can be made by comparing number of cuda cores (only for low memory usage algos).
Power usage (at same clock and number of cuda cores) should be 10-15% less.
12nm production, vs 14nm for the pascal. Less heat and higher clocks should be possible. X16r/x16s/X17/C11 etc. should be around 50% faster than the pacal cards.. My guess 2080ti +50%