Eventually, we will move away from the need to compress music into mp3s and the sound will improve once again.
Yes, all those buying mp3s today will eventually have to buy their music all over again once the new uncompressed formats start to emerge. We will need terrabyte-sized hard drives to hold it all but those are coming as well.
Over the course of my lifetime, there are albums I've bought four times. Vinyl; cassette; compact disk, and finally mp3.