If it'll be anything like the windows version of Steam, it'll likely manage games in parallel with the package manager, thus about as distro-specific as tarball

If it'll be anything like the windows version of Steam, it'll likely manage games in parallel with the package manager, thus about as distro-specific as tarballs. As long as Steam itself is packaged as .deb, .rpm and tarball, it'll probably work as well as other linux games.