"A simple way to forecast the future is to look at what rich people have today [but didn't have 10 years ago]; middle-income people will have something equivalent in 10 years, and poor people will have it in an additional decade."
Indeed the Varian rule was coined by the FT journalist McAfee as you mentioned (https://en.wikipedia.org/wiki/Varian_Rule), though as a counter example, presidents don't really count. Politicians can be wealthy but, like criminals, they're never rich.