Talking to an Air France captain the other day, he said you only tend to see the very young (under 18s sort of thing) and then the very old (post-retirement) on the PPL/club/gliding scene. His theory was something to do with mortgages/cars/wives/work getting on the way in the 20-60 y.o. bracket
So I can't really agree with the assertion that GA will disappear once the lot of you have croaked it (
) I reckon what is happening is people start training at a latter age, so what is possible is that the average/median age will stay about the same, but the experience level may drop.