My hope is that they'll continue supporting multiple audio formats, essentially as an extension of what we have now: downmixing of both Dolby and DTS formats to match whatever speaker configuration the user has. Another all-out format war is not something we need.
My (perhaps mistaken) understanding is that Sony's 4K resolution downloads are essentially full-resolution. If you aren't constrained by needing to stream in realtime, excessively lossy compression isn't necessary. Of course, it'd be more inconvenient than realtime streaming, since you'd have to decide well in advance what you'd want to watch experience. But that's already the case now if you want to play a shiny disc that you don't already have.
The problem is that most people have slow internet connections on average or if they do have a more "high speed" connection it costs an arm and a leg... then there are those pesky monthly data usage caps. So you'll maybe be able to download 1 movie a month and not be able to use your internet for the rest of it without being throttled or made to pay an overage fee.
Yup, a high capacity disc must still be in our future or get ready for severely watered down UHD content in order to get over the hurdles above.