Is there anything definite on Vega 20 being a gaming card? Looks like an Instinct product from the news I can see, which if you look at the Vega compute ability makes perfect sense.
Vega 56 and 64 on a more efficient process i.e 14nm+ would make a strong improvement which for dGPU I would expect to see 1H2018 to tide us over until Navi.
We know just how dedicated AMD were to the APU side, with good reason, so I would guess that we are going to see the first refresh of Vega and Ryzen together on a 14nm+ for the mobile and APU segment which has potential to be the next big win for AMD. They have gained a lot of influence and positive media with Zen and even the current Vega chips are doing awesome at lower power output. There had to be a really good reason for them waiting so long on the mobility and APU parts for Zen and it makes perfect sense for that to be a 14nm+ Ryzen / Vega combo. If 14nm+ gets them to 4.5Ghz+ on the Zen cores and they can get 1060/580 performance from the Vega cores on the top chips they could massively shake up that market.
Navi will coincide with Zen 2 on the 7nm process. With what is in the news I don't see how it can be 1H2018 but I expect to start seeing Navi and Zen 2 2H2018 with Zen 2 / Navi based APU's for 1H2019. I can't see anything suggesting it will be later than that.
Now I am off to buy a lottery ticket...