I like it how the people that were saying "2019 is impossible! 2020 at the earliest" now are saying "2018 is impossible! 2019 at the earliest" :P
I've always been on the 2019 camp , with 2020 as a less likely but possible alternative, People saying 2019 is not possible are simply wrong
People just dont get that console theese days are nothing but little gaming pcs... All they have to do is plan the hardware a year ahead and can come out with another 2 Teraflops more and then do that again and again and again.
By that messurement just count on 10 to 12 teraflops in 2019 with vega64 devkits out now. I mean what else should said devkits be carrying at the moment but a 12,66 teraflop Vega64 Chip. Later they just swap out those devkits for their Navi counterparts wich operate at half the wattage. Since Vega64 is a 300w beast Navi should be able to pull that off at the 150 to 175w target at its 7nm size. And that was the plan all along.
No 20 teraflop monster console or 30 teraflop what some kids wanted to believe.
But make no mistake. Those 10 to 12 teraflops will blow your mind when devs like naughtydog get their hands on that.