The industry will adapt quickly, especially the part that's using multiplatform mainstream engines like UE/Unity.
Lots of new/recent native MacOS releases nowadays: https://store.steampowered.com/macos
Lots of new/recent native MacOS releases nowadays: https://store.steampowered.com/macos
Proton as a project let's valve hedge on the heir apparent OS without upfront developer cost. If the Linux player base grows, developers will follow and valve is poised to remain dominant.