Realtime streaming is a bandwidth pig, but if you had something with 128 GB of storage you could download content in the background at a much lower bandwidth rate. 128kbps, 12 hours a day for a week would give you 300 gigs of offline content.
Netflix could do this with your "My List" of titles and possibly interweave this with some predicted preference stuff and maybe catch a percentage of things you might watch while just browsing (er, vainly searching for something interesting).
At this point you could possibly be watching most of your stuff offline from cache without the need for real time streaming or bandwidth.
I think I've read Netflix say "we'll never do offline streaming" and its probably a licensing/rights issue, although maybe Netflix has some rationale for not doing it to, so that will keep it from happening.
Most STBs and smart TVs don't have storage, but it doesn't seem like adding some flash capability (internally at assembly, or via USB sticks by consumers) would be that expensive.