Goog and Facebook are still safe as hell. Even if you think Facebook is waning, is going tk be hard to dislodge WhatsApp and instagram and I don’t really think Facebook is going away.
Those companies aren't going away any time soon. Heck, IBM, Cisco, Hewlett Packard are all still around, and all still making profits. Doesn't mean they're desirable places to work at all compared to the olden days.