In the end, everything is about money. People will go green when there's money in it. For instance, many utilities try to get you to goto paperless billing to save THEM money. But I bet in the next year or two, they will start charging YOU for those paper bills -then you'll see another big shift to paperless. LOL.
As for the rest of it, eReaders are just about to break under the $100 price point, and now there's epub standards in place, so there will be greater adoption of paperless methods.
On the horizon are technologies for flexible displays, cheap electronics printed onto bio-degradable plastics. Within 5 years its very likely people will be getting adverts and perhaps even newspapers and magazines printed on plastic instead of paper and instead of simple pictures there will be short videos embedded - likely with small plastic batteries right in the bindings to power it all.
I'll just be happy when all magazines come standard with digital versions included for the eReaders.