I see what you mean, but I'm under the impression that Facebook is not "your father's social network" in that it's not even comparable to what MySpace was, neither in numbers nor in qualities.
What I mean is that we are comparing two different beasts, so I'm not sure "it happened to MySpace" is a good telltale sign of what will eventually happen to Facebook.
Not to mention the growing number of people who only use a mobile phone as their gateway to internet services (along with all of the personal info to be gleaned from them) and who spend the vast majority of their time on the web using Facebook.
I've seen this a lot more in countries where internet access wasn't too common until the past 5-10 years and people didn't start out with a less centralized web before apps and closed networks gained popularity.
My partner isn't from the US originally and when I mention how obnoxious it is that Facebook is like the new AOL and I thought we were past this, she reminds me that it's all anyone back home uses for anything and they didn't have internet access back then.
To her and her friends/family back home, the internet basically is Facebook (and occasionally being forced to open their browser app to search for something if they don't just ask around on Facebook). A handful of other apps and defaults define the internet for them and anything else just sounds like too much hassle.
What I mean is that we are comparing two different beasts, so I'm not sure "it happened to MySpace" is a good telltale sign of what will eventually happen to Facebook.