"I predict that 20's, 30's and 40's music (not to mention early rock) will be around long after the New Wave has crashed and disappeared without a trace."

I don't think that is likely that the music that appeared out of the New Wave period (ie late 70s early to mid 80s or so) will completely disappear. Some of the music is so established now. For instance "Every Breath You Take" by the Police is now one of the all time highest grossing songs. But the rest of their canon and Sting's solo work is also well established. My son and his mates (in their mid-teens) all know and play Police material. Likewise we've had youngsters in our club playing "Psycho Killer" by Talking Heads. Those over 60 mostly didn't have a clue what it was but that is a different matter. Elvis Costello's "Shipbuilding" has almost entered the general folk (ducks for use of that word in this context)canon now as has the likes of Joy Division's "Love Will Tear Us Apart". Work by The Jam and Weller's solo stuff is unlikely to be forgotten likewise with The Clash etc. We've had people playing Ian Dury material as well as Squeeze. The list goes on and on. Great pop songs out of the likes of Blondie etc. My son even plays some stuff by 'what are now' more obscure bands. eg "Making Plans For Nigel" by XTC. Just touched the surface here of course.