im gonna go along with this for a second and actually look at a scenario where he's right.
Facebook - Ive had a facebook account for years and for the most part, it has become extremely derivative of what it originally was. the days of receiving Facebook game requests is over, and im not even certain facebook games still exist. everybody use to flock to social media to rant about anything, but now its just "who cares"? the most i see from actual people are family photos. other than that its all just news articles and memes. i dont even use the facebook messenger anymore since Discord has come about, while everyone else uses apps such as Snapchat or Instragram. realistically i can find memes anywhere else, and i could just go to gaming news sites instead of looking at my facebook feed. so yes, i could easily see facebook phasing out by the end of 2021.
Microsoft - they may seem like the biggest company on the planet with Windows, but ask yourself this - what else have they done for you? the windows phone is dead. they are looking to make some serious 180's just to keep Xbox alive. honestly people dont even seem to like Windows much either. 8 was bad, 10 is still getting criticisms and isnt working right. plenty of people are still using 7. they havent really done anything too noteworthy lately. i could see them disappearing in 10 years