> then those complacent middle class will start being less complacent and start demanding more freedom.
They will not start demanding more freedom (only a small minority will do that). They will become increasingly agitated and demand the kind of economic progress they had before, which the CCP won't be able to deliver (the easy, fast, low-debt growth has largely been saturated).
Specifically the CCP | people-of-China socioeconomic pact is based on the country continuing to deliver massive economic gains to the bulk of the population.
Xi has begun a new cultural revolution (just ahead of the curve) because he recognizes it's going to be required to stomp down on the population in order for the CCP to retain its position, as the easy economic gains are well over. The leadership of the CCP recognizes what's inevitable about their context: they either had to let go of power increasingly, or they have to become more totalitarian, as the growth pact begins to falter. What waits for China the next 30 years, is significant demographic erosion, slow growth and epic persistent debt problems (which doesn't mean they aren't going to be a superpower, they are).