http://www.amazon.com/Who-Stole-My-Church-Century/dp/0785230491 This helps me somewhat. I grew up in a Mennonite church, and I was always listening to new Christian music like DCTalk, Carman, MWS, etc. So, I think hymns are still relevant, but it comes down to "Am I willing to worship God through this older/newer music?" My pastor likes to say something like it's not how hard the journey is that matters, but what it is going to take to stop you. I can't remember what he exactly said, but something like that. I like old hymns done in their original key, or if they are given a drum beat. Or if they change the key, that's cool. I don't like it when they speed them up considerably. Then they sound like some cheap hick bluegrass (nothing against bluegrass) ameture festival on PBS gone wrong.
The younger folks (I'm 31, so I fit in both) could learn a lot from the hymns, like why they were written. Fanny Crosby was blind her whole life, yet she wrote some of the best hymns I know. If done by the right people, this could close the age gap between worshipers more.
On the other hand, newer music represents the new generation of Christians. A chance to lead, to praise God in a new way, or to bring revival and repentance to the church. Guys like Keith Green, who would impact generations of Christians long after he died, would bring revival by writing new songs, or putting music to "The Sheep and the Goats". I could go on, but I need to shut up.