I believe that any music can be relevant to today's teenagers. A lot of U2's songs have moral messages in them which are relevant in today's society, and I believe that any music promoting good morals will always be relevant. This is proven by the ongoing popularity of the music of U2, amongst people of all ages.
Yes, U2 still has a relevant message for today's teenagers. U2's sensitive and politically pertinent pop music is still as relevant as it was when U2 was at its height of popularity. Their songs about love still apply to the trials of today's teenagers, and their social consciousness is relevant as well.
The band U2 still has a relevant message for today's teenagers. The songs have a powerful message that transcends time. For instance, the song, Out of Control, is about a boy who feels he has not control over his life. More up to date songs cover the hurricane that devastated New Orleans.
I think U2's fanbase has grown older and many of todays teenagers listen to other musicians and bands. U2 are very known for getting on peoples nerves as well so even if they force people to have their music via iTunes it still doesn't mean teenagers will like them as much as they do other artists. With the ears to shout at U2 will have less impact at passing a relevant message.