In the end of the day, China is a Communist country. Personal wealth does not officially exist. Anything anyone "owns" is with the permission of the Communist Party, which can take it back anytime it wishes.
Essentially, these people are playing the stock market with money they dont really own, in the sense that we in the west own things. Anyone in China who appears to have wealth, has it because they are in favour with the local communist party.
Problem for China, is that eventually it will all come crumbling down. The people will want to really keep the wealth they have earned. As appetite for consumer western style goods grows, they'll want the whole package - the western lifestyle - which includes democracy. They'll want more freedom to chose, more freedom to acquire wealth, a more equal society where merit rather than communist party membership gets you on in the world.
China is also very diverse with different peoples in different parts. When it crashes, and the people want freedom, expect it to fraction into various independent countries ala the soviet bloc.