Good points! A few random thoughts:
I don't really think the music (movie, etc.) industry gives a shit about what sells as long as it sells. It's not an "entertainment-provider" so much as a $ machine. If people still want to buy shit music, they don't have a problem with providing it.
I don't really think that the masses of top-40 types think about what they could be listening to. As an example, I grew up listening to the Beatles and disco mainly, I didn't even hear oldies 'til after high-school graduation. Someone once told me, "If there are only 3 channels on TV, and 2 of 'em go off the air, you know what people will be watching."
Also, um, hip music is for the hip, the masses will always be a bit clueless.
Demographics are changing too, the kids in the future will likely prefer various types of dance music.
Once in a while, something will pop up in the square world that's like a pale, washed-out version of some type of punk, i.e the Strokes (not saying that 1st lp wasn't fun, but it's not punk) or the White Stripes, etc. That's about as good as they can hope for 'til they wake up (as we did) and realize there's better music out there. I can't see most people I've known rockin' out to the Oblivions or Watchband.
The public has blinders on.