So far "GeForce NOW" has just been a service that lets you play your own Steam/Blizzard library on nVidia's servers. The service could shut down and you could still play your games on your own hardware.
nVidia also makes their GameStream software available to users so you can send your own games from your PC to a nVidia console or tablet, or any device running the FOSS Moonlight client. Or you can cast your games using Steam's streaming protocol.
Mind you, I'm not a big nVidia fan for other reasons, but so far they've handled game streaming pretty well. Still, GeForce Now is a beta product so things could always change before (or after) release.