While I'm disappointed Disney is/may be discontinuing the Treasures series, I'm not surprised. Despite a report to the contrary, I think sales volume is playing a role. I remember when the first Disney Treasures came out (Mickey in Living Color, Davy Crockett, Disneyland USA and Silly Symphonies), they sold quickly and were hard to find after only a few weeks of release. Some of the subsequent releases did as well (The Complete Goofy comes to mind right away). I haven't noticed the later waves jumping off the shelves nearly as fast (this is an entirely unscientific observation, mind you).
Also, I think most of the unreleased material Disney has left in the vault appeals mostly to hardcore collectors like us and has limited sales potential to the mainstream consumer. Zorro may be the one exception to that and hopefully we'll see it in a Legacy Collection release one day. I just don't think Disney will be able to move enough silver tins to make future releases viable. When you look at it, even the upcoming Legacy releases are a stretch. Destino is a Disney oddity at best, and though Disneyphiles have a soft spot for Oswald, that silent pre-Mickey rubber hose animation is not going to find favor with audiences accustomed to Nick and Cartoon Network.
The Disney Treasures had a good run while they lasted, but it's time for them to move on.