Crossplay may have been brought to the world's attention by Epic Games and the whole PS4 controversy, but Microsoft and Valve seem to be spearheading the next step in its integration between PC and Xbox One systems, as some leaks suggest.
Valve recently updated Steam's beta build and a sleuth from ResetEra was quick to check out the new code in hopes of finding info on future features. Madjoki seems to have hit a gold vein, as the code yielded results that hint at better integration between Xbox Live and Steam services.
Crossplay between the two services already existed through titles such as Killer Instinct, but the code suggests an integration through Steamworks developer toolset. Should this integration become a reality, developers would find it a whole lot easier to implement crossplay between Steam and Xbox Live in their games. This, in turn, could potentially lead to an influx of new titles that support crossplay between Xbox One and PC.
Then again, this is just a few that reference an open source integration, and they are only present in a beta build at the moment, so ETA for the feature is still unknown. It is also unknown whether it will actually see the light of day at all, since there is no official confirmation from either Valve or Microsoft working on the integration yet.
Considering Microsoft decided to press the attack upon seeing the backlash Sony received from walling off their player base behind a proverbial no-crossplay wall and already pushed for Fortnite crossplay with Nintendo, it is not hard to imagine them doing the same with Valve. This way, Microsoft would have an easier time integrating two of their player bases, from Windows and Xbox One.
Microsoft acquired new developer studios en masse in 2018, presumably in an attempt to catch up with Sony's exclusives. With the new light shed on their crossplay plans, it could be possible that the company will continue down the path of having their own exclusives available on both PC and Xbox One.