Between Proton and WSL we're getting closer to a true "write once run anywhere" world where host platform won't matter so much. Devs will be free to develop with whatever tech stack they like most, make a canonical build, and other platforms will be able to run it.
What's going to be hilarious is that much like dosbox became the best way to run old dos programs even if they might still technically run on windows, wine/proton will be (and sometimes already is) the best way to run many older windows programs. Particularly I'm in love with proton's fullscreen magic that doesn't actually mess with your display mode, so e.g. I can run Touhou games fullscreen in proton with my display at 4k despite them only supporting 480p fullscreen -- running on Windows will try to set my display mode to that with varying success. At some point we'll be running old Windows programs on Windows with wine/proton through WSL.