I'm not that poster or providing any links to substantiate my claims, but I think the writing is already on the wall and Facebook is seeing it. That's why they were investing so much in Instagram, and now also Messenger, even as a web service -- www.messenger.com. The latest is that they're thinking of introducing games on Messenger, slowly making it a platform on its own.
I _think_ that what Facebook is seeing is that social networks as a huge monolith is dying, that youth is abandoning it first in favor of specialized, niche networks. It's common psychology, really. Youth never enjoyed hanging around with their parents. If parents use Facebook to talk, they'd rather pick something else, like Kik.
Google is seeing it with Google+, which turned into a social network for photographers and geeks, so nowadays they mostly just pump out new photography oriented features.
I think they're careful to say it though since it might indicate a weakness in their strategy, a problem for advertisers:
> “I feel photos are the lifeblood of our service,” said Google+ lead Bradley Horowitz during the conference in 2012. “They are the way we can most immediately and viscerally connect as human beings.”
They're careful to say "photos" are the lifeblood, not "photographers".
Anyway, I think that within as little as five years ahead, we'll still see Facebook a very big company, but many smaller services. If that strategy is successful, I think we'll keep seeing Facebook as a big company for the foreseeable future. I don't think they'll be dead in 10 years, definitely not. But I do think people will barely know they're hanging around on Facebook and they'll have apps for all common demographies.