Japan will likely be overtaken by China's Tier 1 cities in terms of GDP per capita

It was only a generation ago that Japan's GDP surpassed the entire GDP of Asia excluding Japan.
Now, cities like Guangzhou and Shenzhen in China, which were on par with Japanese domestic workers 30 years ago, will soon overtake Japan in terms of GDP per capita.
Is it possible for such a dramatic decline and reversal to occur in just a single generation without a war?