There isn´t much fear from China. They are going through a growth face similar to the USA in the early 1900s. The problem is that they haven´t yet hit the stage of their economy where the middle class starts making demands. At some point, healthcare, the environment, worker´s rights, and social rights for children are going to kick in and it will drastically slow down their economy. Right now, they have all the benefits of an economy similar to the west, but without the need to provide any services for their people. That will change soon as the middle-class matures there.
The other thing that is going to kill China is their lack of creativity and their lack of protection for intellectual property. China´s entire economy is based around doing stuff other people do, but cheaper. And that works as long as you have cheap labor. But because China has never honored any type of intellectual property laws, nobody there really tries to be creative, because even if you are the guy that invents something amazing, your neighbor will just do it cheaper and there is nothing you can do. The USA grew in the last century because people who invented and created had a big payoff, that caused more people to want to invent and create. Look at the biggest tech companies in China, all they are is cut-n-paste copies of US companies. Alibaba is exactly what Amazon.com is. When their economy and middle class matures, they will no longer have the cheap labor they have now, and they won´t have a culture of inventors and entrepreneurs like we have.
You want to know when China will start to fail, wait for protests about the environment there or about working conditions. When they have to play by the same economic rules as the rest of the world, their lack of creativity and IP protection will be their downfall.