Well, Facebook has full pockets and a working cash machine. And at least until now the managed to identify threats. For example WhatsApp and Instagram were acquired. When G+ came they copied G+'s circle feature close enough with their contact grouping feature, when Snap didn't want to be acquired they added stories everywhere (WhatsApp, messenger, Facebook)

Yesterday's news tells us that competing with Facebook in the messenger field isn't easy (Google cancelling Allo)

For a long-term strategy we have to see how there diversification (facebook@work, Oculus, ...) works out and how long they can keep printing money.