It's easy to predict that companies will fail, because most do in the end. It's very rare for companies to survive for long periods of time. Just look at the fortune 500 over time. It changes, massively, from decade to decade. If anything that trend is accelerating: companies grow faster and disappear faster as well. So, predicting that neither e.g. Google nor Facebook will be around a decade or two from now is not that unimaginable. Maybe they'll find a way to survive. Maybe they won't.
My bet would be Facebook might disappear and Google has more of a chance of diversifying their business enough that they may survive. The reason is that ad driven business models are long term problematic for both but Google at least has alternate revenue streams (e.g. cloud infrastructure revenue, mobile phone revenue, content subscriptions, b2b sales for analytics, development tooling, etc). They have a much more diverse portfolio of products and services than Facebook. And that's discounting the stuff they do under the Alphabet umbrella. Facebook has just ads. Ads on Facebook, Instagram, Whatsapp, ....
The odds are stacked against pure ad driven business models. It's a race to the bottom. There's privacy legislation, browsers are being upgraded to counter tracking, and users are slowly getting a clue about it being kind of scary that big companies know a lot of shit about them. Add to that the stream of negative news about them and you are looking at serious challenges to what is the only business model Facebook ever had: create addictive engagement driven properties and claim as much time of their users as possible on it so they can measure what they do and feed them ads, fake news, sponsored content, and other stuff 24x7.
Facebook needs to diversify their revenue streams and not just their user facing properties. If they fail to do that, they'll peak and eventually decline.
My guess is that the pressure on Mark Zuckerberg to resign will keep on building until he eventually resigns. Then if they fail to change course under a new CEO, they could suffer the exact same fate as Yahoo where shareholders milk the existing business dry and eventually sell whatever remains for scraps. In the case of Yahoo, this only took a decade or so.