Oh no, I'm just going to have to hope they won't ask for it before Proton (or something) starts supporting it :)
But you are right, a time may come when they will want Windows. Although my wife's computer runs it (needs it as a teacher), so they may use that for Win only stuff. I'll deal with it when the time comes.
I could do a VM with GPU pass-through and Steam client... Although that may also turn out to be more than I'm willing to invest (and essentially you still run Windows). Or maybe I'll dual boot...