As incomes rise in China people will demand other things from the government than food, shelter and a comfortable middle class life. Hong Kong was ahead of the rest of China since they have been living pretty liberal under UK rule and were more prosperous. Whatever they do in Hong Kong now will not stop from things happening all over China at a given point.
China is where the USA was in the 1950s; lots of industrial growth but lots of pollutions, a population happy about all the new wealth and not willing to protest.
The two countries are absolutely incomparable on these particular points. Prosperity alone does not quell protests, most protests in the U.S. are decidedly bourgeois.