Maybe I missed something, but he seems to be using the same math as the guy who projected his baby would gain a weight of a trillion pounds if the rate of increase remains constant.
Not only that, it kinda implies that everyone wants to be a Sato, otherwise they could chose the other surname upon marriage. Which people would most likely do if it is too common. Given this assumption, the option to keep your maiden name wouldn't help (but should still be there).
PugJesus