New references have been discovered within Steam and shared on Reddit. These references indicate that Valve may be implementing compatibility tools that “allow you to play games from your library that were built for other operating systems”. It looks like there will be several options available too, allowing users to force compatibility for all games, or just limit it to ones that have been specifically verified.

On the surface, this sounds like a form of Wine wrapper, which has been used in the past to get Windows games running on Mac and Linux with varying degrees of success. I’ve only ever tried this technique myself once with Skyrim on a MacBook. With Valve’s backing, a lot of the hassle would be taken out of the equation, although issues may still persist for some games.