To sum it up; looking around you don't see people in coffee shops using iPads (or any tablets)--it's all laptops. Even though iPads have outsold laptops by a significant margin for years now.
As a bit of a tangent (also mentioned by him); anyone who is productive on an iPad Pro uses a keyboard. Apple has refused to add touchscreens to laptops, but iPads with keyboard suffer this exact problem. So something still needs to evolve.
I see iPads/phones replacing the entertainment needs a general purpose computer used to fill and maybe Apple gets out of general purpose computing. This is also happening for "light" computing needs in business; like POS and inventory. But I don't see any sign that a PC going away at all for workhorse tasks just yet.
[1] https://daringfireball.net/linked/2018/06/13/ipad-trackpad-i...