It's hard to say, really, because the music industry is a very different thing from what it was 50 years ago. Not very many people are familiar with artists like Bing Crosby, The Andrews Sisters, etc. And those are some of the MORE popular artists of their era. But since the 1960's, the quality of sound has grown tremendously and music like The Beatles is still widely available and accessible today. But again, the most popular of their era. Still, there isn't MUCH further we could go in terms of providing better quality sound. So unless there's some new and revolutionary way to record sound in such a way that it'll sound even better to the human ear, like it burrows right into your brain, I doubt the quality of current music will ever be considered, "retro sounding" as far as how crisp and clear and deep it is.
Honestly, it doesn't matter to me. All I care about is my own blood line. When I have kids, I'll make sure they're listening to Dream Theater. The spirit will carry on.