I actually think there's a fairly significant polemical error in original article. He says:
Hence, by 2050 or earlier, when they once again become the two largest economies, we will return to the historic norm of the past 2000 years. And, in history, it is easier to return to historical norms than to deviate from them.
And for this to work as a proof of anything, we have to ignore some substantially altered international interrelations and new world environments. Air travel, television, phone calls, the existence of international media... the end of western domination of world history is definitely on the cards, but it doesn't constitute much of a "return" to something older. The western egg won't get back into the pre-industrial chicken without some considerable squawking.
However, the *new* world condition of a global voice for China (and India)... that will be interesting.
Moribund cultures seeking more moribundity and now with the economic might to enforce it? If we are indeed returning to a prior historical condition, perhaps they will give up their industrial might.