Netflix released some estimates from their splitting the streaming and DVD businesses:
Clearly people have overwhelmingly chosen streaming-only vs. dvd-only. The numbers match up pretty well from what Netflix estimated at the end of July, with a small error in how many people would stick with DVD-only. Anecdotally, I think some streaming-only people are still watching DVDs, just using services like Redbox. Some people who dropped Netflix entirely also were probably lured by Redbox.
That said, I think this is a watershed for streaming. If you are in production on a film right now, you need to be planning for a world where a large and growing audience can ONLY see your film at home via streaming.