They got a bunch of gold over the past decade, that idea is plausible.
This can also be a reason for them to cut ways to get yuan exchanged for BTC.
http://www.zerohedge.com/contributed/2012-21-22/will-china-make-yuan-gold-backed-currency
The problem with the Chinese just backing CNY with Gold is the fluctuation of Gold Prices and finite amount of Gold. The Chinese government has to oversea 1 BILLION people. If you peg your currency to Gold like we use to do. Your going to run into some problems of having enough money supply. I believe China is lacking innovation. No country can just become great in manufacturing and holding Gold. Its all about innovation and create new money. Besides China will lose a great deal from the US Dollar losing its World Currency Status. You tank the US economy. China will have nothing in terms of manufacturing. The Chinese are solely dependent on Americans buying and the West.
The chinese might have surplus but how long will that last? Innovation in manufacturing will eventually make people obsolete. When it will be easier and cheaper to hire robots to do work. China needs to wake up and start developing innovation tech instead of relying on manufacturing. You can horde all resources you want. Although when the income that coming slows down and you don't have any new innovation that when your in trouble.
The Chinese already have polluted 92% of their lands. Importing food for 1 Billion people can get very expensive.