I won't hazard a guess as to when CDs will completely disappear (probably never) but I do expect them to give way to electronic distribution. We're almost ready to see movies distributed this way but network bandwidth is restricting that market right now.
Here's what I WISH would happen with music distribution and this assumes we can overcome the DRM issues. Music labels could store the originals in a suitable hi rez format and allow buyers to pick the format and resolution they wanted to download. The product could then be sent in full resolution or converted and downsampled on the fly to the selected format and resolution. The fly in this ointment (so to speak) is what will be the incentive for labels to put the time into producing well recorded product if most buyers are downloading at a resolution that won't show the advantage of the extra time and effort.
I must admit that the Sonos controller looks really cool and intrigues me. I get really tired of putting on glasses so I can squint at the track list (usually printed in gray on black or some other idiotic combination) on a new CD to figure out what song is playing. They're also going to have to figure out how to distribute albums that have no gaps between tracks (e.g., live albums and some classical) - that's very irritating (at least to me). EAC-type image rips to wav with associated .cue files are one way to get around this.
Note that I see this as different than the change from vinyl to CD. That was a fundamental change in the way that music was recorded and the carrier that it was distributed on. The change from CD/SACD/DVD-A to hard drive is much less dramatic. Essentially the data stays the same, it's just distributed differently.
Note also that I still listen to LPs and don't expect this will change. Whether I rip my CDs and switch to electronic distribution will probably be determined by whether the industry can overcome the shortcomings I mentioned above.
Dick