It may prove to be illegal if you dispose of the CDs and keep the music on your HD or other devices. It's almost certainly illegal if you sell them, give them to a friend, or even donate to a charity who may resell them. I plan to keep my CDs to remain legal. And when there's a new music format to replace mp3/aac or whatever, I'll be able to delete the old files and rip new ones, legally I assume.
I think you are correct, and I have thought about that.
By the time I'm ready to 'dispose' of my CDs, by whatever means, I don't think the record labels will be taking any big hit. Those CDs would have been purchased and 'off the market' for many decades. I don't necessarily mean 'out of print', just that my CDs have been 'locked up' and unavailable to others for decades - anyone looking for that CD in the past 30 years would have had to buy it elsewhere.
Is it technically illegal - yes, I think so. From a pragmatic stand, it would be very, very small potatoes if they lost a potential sale 30 years later (different from buying, ripping, and immediately re-selling CDs in quantity), and I can't imagine any repercussions. I do believe in doing the right thing, even though the record labels have screwed us royally, but my 'guilt factor' on this would be really, really small. In an abundance of caution, and because it would be easy, before I got rid of the CDs, I'd snap pictures of piles of them, just as some proof that I did possess them at one time. Just store the pics on the HD with the music.
Also probably illegal - I occasionally get CDs from the Library, and strictly for convenience (I don't even have my audio CD player hooked into my stereo anymore), I rip them, so I can listen through my computer-player set up or portable player. But after I've listened a few times, I delete the files - it may be past the 3 week limit if I just didn't get around to listening, but I do delete them after what I consider an equivalent time.
-ERD50