None of these "features" require OS support as far as I'm aware (Steam on Linux doesn't need any special privileged bits to work, Steam on Windows seems pretty standalone, etc). Their model has not required platform-level DRM and hopefully they're not going to change directions on that. It's a big headache that doesn't actually "solve" piracy, and they haven't needed it so far, so I'd be surprised if they decided they needed it now.