I don't think they'll go away for quite some time either, unless some new format comes along and totally wipes the floor with CDs. I don't see that happening either. CD isn't exactly 8 track.
I do think accessibility of buying CDs in person will dwindle significantly though. Been to Best Buy lately?
Most stores that sell CDs are way overpriced, and I think they're pricing themselves out of the market. FYE and Barnes &Noble sell the new Pink Floyd CDs for $17.99 or so. Best Buy has them for $11.99. FYE's saving grace for me was used CDs. They jacked the prices up on those too. Why buy a used CD for $9 when Best Buy has a new copy for $10? Same can be said for movies. How they're still in business and why people continue to shop there is beyond my comprehension. It's not like they offer extraordinary service.
I think Amazon or a similar place will have CDs for a very long time. I'd imagine they currently dominate the market anyway. Best Buy has a lot of titles online for pretty good prices, but I never think of checking them out when buying.
If we go to a download only system, I'd like to see the artists offer this themselves from their own websites. A lot of them currently sell concert downloads through their websites, so why not studio albums as well?
Check out livemetallica.com to see what I'm talking about. You can download in mp3 or FLAC, and you can download CD labels, cover art, etc. only a matter of time before an artist who offers this's contract ends and they say screw the record companies.