Well I'm in my thirties so am out of touch as we are mainly taking about what is popular, which tends to be driven by teens to people in their early twenties.
My hope though is that the internet democratises music and we end up without dominating genres and superstars but much more diversity and the ability for niche musicians to make a living. But then kids will always listen to what other kids are listening to. if we look at the cycles then hip hop &and r&b probably have another decade as the dominant music, but as I said technology might shake things up.