And I would be surprised if this prediction is even remotely accurate. Do you use Facebook? It is increasingly becoming the only website you need to keep in touch with your contacts/friends and it is the only website that I have ever encountered that actually makes Google search engine less relevant. My friends no longer tell me to "Google" something that comes up in a conversation. They just post the link with a description of why they might like it to their profiles.
Last but not least: they have done a really, really nice job with the website. As far as Web 2.0 apps go, I would put facebook second only to gmail.