I have the feeling facebook is slowly dying, but I'm probably wrongly generalizing my own experience (is this called a "false consensus bias"?)
My sister (early 40s) and her peers are still using it on a regular basis, but the content could easily be on twitter or instagram.
The real demographic that is in love with it is my parents' generation, ~67+. They follow a lot of the '%city% then and now' and other nostalgic groups. Along with those, their feeds are filled with goofy videos that were going around a while ago.
I don't see Facebook going the way of myspace in the near future, but I do think they'll have to shift their focus a little if they want to draw us back in.
What I don't understand is why facebook isn't going head first into online dating. They already have a lot of information on everybody -- where a lot of us like to eat, locations we frequent, events we like, etc. For a lot of us the data would be slightly outdated, but I bet they could give some solid suggestions.
That's something I really don't see happening.
Only people I know ever mentioning facebook are (as mentioned in the other reply) middle-aged upwards.
They're not leaving Facebook, just switching from one Facebook property to another.
It's strictly a loss for Facebook, unless they can figure out how to monetize Whatsapp to the same extent as their main platform.