And we all know that what teenagers believe is true...
It might be over for teenagers who want whatever is cool and new, but I think Facebook has gotten a position in society that MySpace never reached, and I don't see the influence of Facebook diminishing in the immediate future. Think of things like Twitter, Pinterest, Instagram, etc.; Facebook has simply found ways to link to those and make them content creators for Facebook.
I rather like Facebook. Sure, some people post useless crap on there, and stuff I disagree with, but I can choose not to let that stuff keep me from the benefits of Facebook.