I bet though .. as much as we would love a "full Disney library" that Disney will either:
1) Trickle things like the classic movies into it ("coming next month - Peter Pan. Coming in June - Song of the South (J/k)")
2) Rotate the old and new content in and out of service - thus encouraging customers to "buy" the digital copies for the permanent streaming option. Even though Disney obviously doesn't have to pay any licensing fees on their own content -- I could see them still doing this to keep the content fresh.
It keeps customers on the hook too as constant new (but old) content is released.
I mean right now I have quite a collection of Disney movies on MoviesAnywhere thanks to all the multi-packs I've bought over the past 10 years or so - both classic and new movies. I like having the digital copies of Beauty and the Beast, MOnsters Inc., Sword and the Stone. to watch whenever I want on my smart TV or device without a physical disc.
But if new movies will "live" on
Disney+ forever -- I have no incentive to ever "buy" a physical or digital copy again if all I have to do is subscribe and have access to the whole library with the click of a button. I mean I am sure it will be easier/cheaper in the future to just stream movies right to your car -- no need for DVDs. (the main reason I get them .. for those long car trips with the kids)
But maybe that is just the future -- I mean who buys physical or MP3 music anymore? Just pay for a streaming service.