On the topic, overtaking US in trading may not mean that much in reality. It does not indicate that China wins or US loses, since it is not a zero sum game, and much of the profit in these trades goes to the states, Europe and other nations such as Japan and South Korea. The sheer size of the Chinese economy has its own advantage, but it also makes it harder for China to follow the footstep of smaller economies such as South Korea, as it is almost impossible for China to completely fuel its economy by simply climbing up the supply chain.
One good sign is that Chinese domestic consumption is soaring. The Chinese online retailing giant alibaba.com just announced that sales on its taobao.com and tmall.com reached the 1 trillion RMB ($ 157 billion) mark at the end of November. This also give international companies a lot of opportunities, for instance Denmark company JACK & JONES is the only company selling more than 127 million RMB ($ 20 million) in 24 hours on the singles' day through its store on tmall.com, and logistics giants DHL, UPS and FedEx are now permitted to enter the Chinese domestic market to take a big chunk of the share. I've always had the impression that domestic consumption in China, or tertiary sector for that matter, was seriously underestimated, and these recent numbers on Chinese spending power made me further believe so.