I think that music retailers ought to make a digital push. Perhaps not ditch physical CD's out completely, but certainly push for digital sales...and here's how I would do it.
Let's just say you're at one of these stores buying something and you stumble upon the music section.
Imagine a computer system that allows you to register to a digital store and then be able to download and sync those songs almost immediately.
All you would need to do that are a hard drive, a flash drive or an MP3 player with its USB cable. You register for the service, you pick the songs/albums you want to download and within minutes, they're yours. For people who just purchased a music player for the first time and don't know how to use one can have the option of running through the instructions with how to upload those songs.
This is in the case that you're on the run and don't really have time to do it at your own house.
Music shelves have decreased in size anyway, so with that said, if you open this system, you'd have an "endless shelf".