Geoffkait, Dynamic range is only one factor in sound quality and not all cds are overly dynamically compressed, nor will all cds be overly compressed in the future.
If you listen to grammy type pop music, compression is a problem. However, there are many cds released in more adult oriented genres that are not overly dynamically compressed. I'm surprised you didn't know that. So the problem of dynamic compression is not an issue on many cds and SACDs.
Meanwhile, new cd players are improving many different factors in sound quality rapidly, and we are moving from the era of cd on to hi rez digital, which holds the promise of even greater improvements in sound quality. Not all hi rez files or hi rez players will sound better, many will though.
Rbbert, I agree about wow and flutter. Misaligned tape heads (most weren't adjustable) and particles shedding from the tape gumming up the tape path also contributed to poor sound quality for cassettes.