I don't know who or what will stop China, but there are some possibilities:

• a very bad demography killing the internal consumption leading to economic decline https://www.japantimes.co.jp/news/2020/08/24/business/economy-business/china-investors-record-defaults/#.X0PEnWgzaJM
• a natural catastrophe like that (leading to starvation): https://threadreaderapp.com/thread/1287836332883050498.html
• the dislocation of western production facilities (due to Trump or Corona or cheaper production in countries like Vietnam)
• an accelerating capital flight out of China leading to an increasing inflation of the Yuan
• an internal power battle or putsch against Xi Jinping
• an uncontrollable uprising in Xinjiang
• an extreme shortage of oil (e.g. by a war between Iran and Saudi-Barbaria) leading to a shortage of food (China needs to import 10 million barrels of oil per day)

I don't know what will happen. There are just too many risk factors affecting China. I think China is in a position where the Soviet Union was in around 1988 😕