The former is a given whenever AMD (or Nvidia) launches a new graphics cards, though Linux drivers sometimes lag behind. A recent example is the Radeon RX 590. As Phoronix lamented, it didn't play nice on Linux at launch, and it took a few weeks before it finally did.
That shouldn't be the case when the Radeon VII launches. Jason Evangehlo, a former marketing specialist for AMD's Radeon division, wrote on Forbes that he reached out AMD's PR people over the weekend and asked if the Radeon VII would be "gaming ready on day one right out of the box."
The answer was an "emphatic 'yes'," Jason says. That means Linux driver availability and presumably proper testing beforehand to ensure it works better than the Radeon RX 590 did at launch.
According to Steam's hardware and software survey for the month of December, the overwhelming majority of gamers on Valve's platform use Windows—nine out of 10, based on the percentages. Less than 1 percent of Steam users run Linux.
While there is huge gap, there has been a definite push to promote Linux as a viable alternative to Windows. In addition, the disparity in supported games isn't quite as large—roughly 20 percent of the games on Steam support Linux. As Jason recently noted, around 1,000 games on GOG run natively on Linux, and more than twice as many do in the Humble store.
It's a good sign for Linux users that AMD is aiming to get things right on launch day. AMD also recently said it will have enough Radeon VII cards to meet demand, in the wake of a report suggesting that it would be in short supply. How high the demand actually ends up being, though, is a whole other topic.