Japan had 120 million people in the 80's. China is currently at 1.35 billion. There were a million new millionaires created in China in 2014. I'm not sure that the Japan situation compares to China very well.
I too am skeptical of the Japan comparison. China is both a very densely populated but also an extremely populous country and I think its just natural that a lot of Chinese will want to leave for less-densely populated places. Just the number of people involved makes this a problem unlike any other we've seen in history; how many tens of millions of Chinese millionaires now have the option of picking up and leaving their homeland? The scale of the migration is larger but the size of west coast cities isn't; certainly not by a factor of 10.
Anyways, we've all heard "its different this time" before, and it never is.