If it can't compete with Titan X or 1080 Ti, why would they name it RX Vega and not RX 580/590? And Volta should have x70 running as fast 1080 Ti! Making fun of it with a chip twice as large would be just bad marketing. Also 1080 Ti price surprises me greatly. It could be $800 (and have a $900 FE) if big Vega is really not a threat, and people would still buy it. I doubt we will see top Vega under $600 ... it's big and expensive, so it won't be able to undercut nVidia cards by that much.
I'm still cautiously optimistic, because I know most of their R&D cash was probably spent on Ryzen, but I think another 980 Ti vs Fury X is perfectly doable.
People were saying how Fury X is inferior. But if you look at it today, sure, it can't beat GTX 1080, but there are quite a lot of games where Fury X beats GTX 1070. And where it doesn't, it has a lot higher minimal framerate compared to GTX 980Ti. And I'm not talking about DX12/Vulkan games only. If it's roughly a GTX 1080Ti competetor, that's already job done well.