Is there any future for teen popstars today?

I am wondering whether there is any future for celebrities like Hilary Duff, Rihanna etc. You know what I mean. But what I don't get is what they are going to do 20 years down the road. Obviously they would have grown up and cannot sing the teenage songs they used to sing. Maybe they can act but the shows they acted are all those teenage comedies, not serious stuff and that would be typecast. So what can these celebrities become after they grow up. Some of them can't even sing! This is a question I've been pondering. Will they just fade into oblivion or will they continue to be like Madonna, who prances around like a twenty year old even though we know she went for Botox? What will happen to them? 10 points to the most mature answer. Thanks to anyone who answers my question. You make a fourteen year old more knowledgable. Thanks!