Think of how Microsoft quickly killed the Linux based netbooks, when they really started paying attention, then the new tablets market did the rest.
It's tough to say. Annoying Linux people like me tend to have horse-blinders on towards the rest of the world (hence the constant meme of the "Year of the Linux Desktop"), so it's tough for me to speculate with any kind of objectivity.
That said, Steam Decks seem to be selling pretty well, and people don't seem to mind the SteamOS part of it. I think that there's a chance that Linux will be a permanent fixture for Valve now. I don't think they're going to overtake Microsoft, but I think that "Steam Deck" is a viable enough of a target platform for game studios to develop against that it's here to stay.
I think part of that is because of its form factor already limiting the device. Like how Android and iOS are fine on a phone or tablet, but I doubt most people would want it on a desktop computer.
Not talking about the Linux part, but the real test with the Deck is whether or not it'll stay a target platform with its low performance and Valve not releasing a Deck 2 anytime soon. Valve's Steam Deck verified program already checks performance on games and newer games like Horizon Forbidden West and Indiana Jones and the Great Circle are failing.
I think especially for indie games, which are typically less demanding than the big new AAA shoot-at-stuff games, the Steam Deck might be an "unofficial standard" for quite awhile.
Though I don't work in the games industry, so I'm talking out of my ass. Again, I'm an annoying Linux person so take what I say with a grain of salt.
