... rest of us, the idea that you can count on the fact that a business, organisation, or individual can make or receive PSTN calls will no longer be 90%, or even 50%, assured. (I suspect the breakdown point is somewhere close to 71%, at which point the chance that any _two_ entities have phone access reaches 50%.)
And once that point is reached, things will change very, very quickly. The flipside of network growth dynamics, with their positive-feedback cycles, is network _decline_.
Generalistic and moderated instance.