The article seems to believe that gaming on Linux is on some kind of death clock unless Proton can start gaining traction. I beg to disagree. Linux developers happen to like gaming, so we'll continue to see improvements in that space, regardless of popular demand.
One might argue that Proton, specifically, is a venture funded by Valve. That's partly true, but Valve is a very bottom-up company. Valve's developers are choosing to work on Proton because they want to. Even if Gabe Newell himself (or, more likely, some successor) yanks the reigns away and drops support for Proton, many of those same developers are likely to continue working on the project in their own personal time.
There's likely to be an opinionated stance that stops old work flat. Like when Ubuntu killed 32 bit support last year, leaving most compatibility guides useless.