My opinion: I think it won't catch on as windows is too bloated and doesn't bring much advantage to the table. As a matter of fact i got a RPI just to have a standalone linux box.
Proton is an amazing project. I hope it will lead to more Linux Steam users, and consiquently more 1st party support, because I'm sure MS will do everything in their power to make Proton less effective and reliable than it is today over time.
And that's the beauty of Linux, it runs from mini devices to very very heavy supercomputers. I hope one day Steam will be more prevalent on Linux.
It's about time MS is squeezed out the same way they squeezed Netscape out.