OK, I have a little experience in this (journo for a Aus national rock mag in the 80s).
JJJ staterd as 2JJ, with a mandate to play 'youth' music, and that continues today (fab trivia folks: the first song they played was Skyhooks' 'You Just Like Me Cos I'm Good In Bed'!). The thing to keep in mind is that the station, and now national network, is Government funded, so it doesn't have to bend (so much) to commercial pressures, especially as much as other rock stations do. So this becomes a banchmark because of those imagined freedoms, that the choices by the audience are free of
As is the way with 'youf', they aren't going to listen to their dads' music. So they might listen to rock, but it has to be 'alternative', not something yer dad would like. And of course, each person picks up the songs of the moment and adds them to their own personal soundtrack of their lives.
What these 'kids' listen to is rock, just a bit different, just as there's a difference between 'As You Like It' and 'Blithe Spirit'. Have a listen to this, I'm old and I think this is a great song from Eskimo Joe. It appeared on the 2009 JJJ Hot 100 at 65. It's about the death of Heath Ledger, and being alone far from home.
[yt]http://www.youtube.com/watch?v=zI9GWamslKU[/yt]
Now Eskimo Joe might be alternative, but they sure are rock. Listen to that middle section and the choppy rhythms. Good stuff.
To put it another way, I've been on a bit of a Who kick, and I saw an interview with Roger Daltrey, and he said "Yeah, I think rock is dead". That was 1970. Its best years were ahead of it. It changes, and always will.
TL: DR: Is rock dead? No.