I don't think so. And even if it would be the case, that one game would not compensate for the rest 99,999999% of games.
Not necessarily, because most games are built using a game engine, such as Unreal, Frostbite, Unity, etc.
Those Engines can be built/played using DX12.1, or Vulkan, so under RX Vega can easily yield greater gaming results. Additionally, if those engines convert to 16bit (something that Nvidia has to emulate, & can not do natively) you will see 200% increase in those operations, which can effects frames by as much as 30%.
Vulkan, DX12 and 64bit Windows are bringing in a new era of Gaming and it seems to me that AMD is on top of it using advanced hardware. I can easily see RX Vega getting updates (over years) that increase performance in games engines.
We'll know general performance of RX in a few minutes/hours. But given what we already know, Vega looks to be a hit, even if it's performance is not max.