Considering Gabe is ex-microsoft and wants to distance himself as much as possible from them, I highly doubt that'd work, he'd go down fighting at the very least.
Does he want to distance himself? Gabe said he learned more in his short months-long tenure at MS than he did in the rest of his academic career. He dropped out of Harvard, mind you.
He modeled his entire company off of MS. He even adopted their primary strategy, buy, polish and package. It's literally just embrace, extend, extinguish all over. Balmer taught him very well.
I really don't get why people think he's all that different from any other billionaire. He got there by buying out competition, and if they wouldn't sell, theft and litigation.
Not saying he's different from other rich people, but Valve developing both SteamOS and Proton is a clear message they don't want to rely on Microsoft and their software.
Microsoft doesn't want to rely on licensed software every time they install their programs either. Again, Valve taking a queue from MS. And that's fine BTW, the whole industry follows MS.
Moreover the real issue, the difference in computing cost between running Win10 with all the unnecessary boost vs Linux is massive. Had they used Windows it would've costed more to be able to run less.
As to being reliant on Windows, that's been their standard most of their history. Steam was Windows based. If Windows were to go ahead with making a stripped down Windows OS that was specific to gaming, such as the one demoed in a code jam earlier this year, you can bet steam would be selling that version of Windows direct from their store, and likely have a easy tool ready to use to install it to your deck. They would probably offer it as an installation option too. Why not? There's no good reason they shouldn't. The whole verified question goes out the window. That's huge. But again, MS controls that situation, not Valve. They're still reliant on MS in major ways.