That was the idea. I'm not Wolfram Alpha, I'm a human having a conversation. I didn't make any predictions about the future, I'm just expressing my own personal take on the situation. I'm sure I'm going to get down-modded to hell for this especially since you've been up-modded pretty high for contributing basically nothing.
"Just because the world around you looks one way doesn't mean it's the same everywhere."
The ironic part about your AOL/ICQ/MSN example is that, like Facebook, there are network effects. I used ICQ pretty much right up until nobody else did. People are communicating by Facebook so much that even though I don't use it much, if I want to be in the loop that is where I need to go. There are 250 million people communicating on Facebook -- clearly there's a lot less need to communicate by email.
My own personal experience is that for the average user trying to communicate for non-business means, they get a far better experience from other tools than from email.
Now, of course, this all just my personal option. If you want some actual data, you won't find it on hacker news.
When I was in college I could have made the claim that AOL Instant Messenger would become the 'one true' messenger because everyone I knew was on it... while in the rest of the world people were mostly using things like ICQ and/or MSN Messenger.
Just because the world around you looks one way doesn't mean it's the same everywhere. Just because a large number of people use and interact with Twitter doesn't mean that everyone does or that everyone even knows what it is for that matter.