As we have seen with Jack Ma, maybe the Chinese government is afraid of rich billionaires getting influence over the people. Business owners and journalists still just disappear, but would that be possible if a large group of billionaires unites their voices? I don't know, but it is hard to play a type of opposition role as they just destroy your life. Jack Ma was kicked in the ass just for raising his voice. If they can kick his ass, they can probably kick everyone's ass, but how would that change? Who has the power in the state to establish more democratic processes? It is hard to imagine that that could happen anytime soon in China. At the same time the government knows they have to allow for innovation or else they will lose against global competition.
I would say that they wouldn't care even if 100+ billionaires end up saying something. I mean it is obvious that they have a lot of power over people and they do not care if rich people start talking, they would just jail them anyway as soon as they get their hands on them. I would say only possible way for those rich people to talk and make a stand is taking their money out of china and putting it in USA or some other place that is safe, which we all know is not possible since China would not let them take all of their profits outside of China anyway.
So, they can't really talk and be safe, they will be in danger and that has been the case for most Chinese people who criticize china anyway. It is a dictatorship that kills anyone who go against them, so I doubt anyone could make any change.