If you look at History China has always came up only to be knocked back down by themselves. I'm personaly so damn tired of people on forums being all "Doom & Gloom", if China became powerful, it really means nothing at all, other than America, Russia and other western countries wouldn't be the only extremely powerful nations anymore.
China does not have nearly as much global influence on the world in all forms of media as America to completely ever take it over. They are heavily depended on products from other countries. China may hate Japan but i bet every single citizen owns a Japanese product. Japan was expected to become more powerful than the western nations also once upon a time ago because of how quickly they rose up, and what happened? Sony just bought Columbia pictures, Japan never became the world power it was projected to be, and America lived on.
The only thing worse than the doom & gloomers are the ones who actualy want China to take over the world lol. Also for those talking about wars? that will most likely not happen China is depended on the stability of the economy in America & western nations.