To me the calculation is simple: the producers will always take all of the money for streaming, whoever actually runs the front end, and they can't do that for DVDs. Streaming might, over time, kill the DVD-by-mail business, but I imagine there will long be a pretty decent market for "get every title ever sold delivered to your door in 24 hours for one low monthly fee" when the competition will likely be a set of competing services that don't have any kind of comprehensive catalog.
Netflix would be insane to abandon their core business. The first sale doctrine means they can make money doing that, and offer a stable product to customers. In streaming, the content producers are always going to just take all the money with high license fees.
