Mainichi (Google Translate version in English) reports that Professor Hiroshi Yoshida of Tohuku University in Sendai, Japan argues that the most common surname, Sato, will be come universal by the year 2531. Because married couples adopt the same surname, Sato, which currently constitutes 1.529% of the population, will only increase over time.
Professor Yoshida urges that couples keep distinct surnames in order to stave off the coming Satopocalypse. But he also notes that due to declining population, although everyone in Japan will be a Sato by 3310, that's only 22 people total.
-via Spoon & Tamago