There are actually some music Blu-ray Discs out there, and there should be more on the way. There is some classical stuff, and Neil Young has a boxed set available. Do a search on Amazon for "Blu-ray audio" and you'll see some titles.
I am hoping for this to take off, because I think it has a chance to be more successful than SACD or DVD-A. The BD video specs already allow for multichannel audio at up to 24/192, and there's plenty of space, so if they just produce the discs to work with this, the hardware support will be there as long as they keep making the movie players (and PS3s). It won't be some add-on spec like it was with DVD-A. These discs can be played on a computer, and that's something SACD could never do (by design, of course).
There is some discussion about a new BD audio spec that would allow for a player without video, but the discs would still be compatible with current BD video players. Nonetheless, I think having video on the discs can be helpful for marketing, if nothing else.