Steam's new disclaimer reminds everyone that you don't actually own your games, GOG moves in for the killshot: Its offline installers 'cannot be taken away from you'
This has literally always been the case with Steam, the only difference is that people are told up front now. Things will likely continue to operate exactly the same as it has until now, I doubt Valve wants to disrupt the giant money train they have.
As far as I know there is no mandatory DRM on Steam either, so if a publisher wants to they can just make their game be portable and not require Steam to even be installed. Pretty sure all the re-releases that use DOSBox or ScummVM are like this, for example.
Yeah there are loads of DRM free games on steam (mostly indies of course). Steam just offers a very basic (and easily bypassable if you know how) DRM to devs/publishers but they absolutely don't need to use it.