Volta will be very likely launched/available for the comsumer market in Q1 2018, early Q2 2018 the latest. And the coming up card will be again around 70% faster as its predecessor, the GTX1080.
Navi being available in Q3 2018 is highly doubtable. AMD wants to use 7nm and since a new and smaller process usually works fine for small chips like DRAM or smartphone-SOCs, huge GPUs are completely different beasts to handle. They will surely try to catch the christmas market in 2018, but we'll see if yield rates are going to be high enough for more than a bunch of show cards. Or if they sell it first exclusivly to the automotive market like NVidia is doing it with Volta now.
Navi being available in Q3 2018 is highly doubtable. AMD wants to use 7nm and since a new and smaller process usually works fine for small chips like DRAM or smartphone-SOCs, huge GPUs are completely different beasts to handle. They will surely try to catch the christmas market in 2018, but we'll see if yield rates are going to be high enough for more than a bunch of show cards. Or if they sell it first exclusivly to the automotive market like NVidia is doing it with Volta now.