Adjust GDP for PPP (Basically, factor in cost of living, power of currencies) ; and the Chinese economy by sheer size is the largest in the world, in fact it surpassed America a few months ago.
Despite this, PPP per capita is still 1/4 of the US's. There are things China must accomplish if they are to establish themselves as a superpower. Although they have millions of skilled-workers, China needs to attract foreign talent (Or even Chinese students whom studied abroad) are still needed.
China's huge ass population looks as if it were a blessing at a moment, however this is a double edged sword; and due to the remaining effects of the now repealed one child policy they are looking at a lot of old people. The drain this will have on the economy is not to be scoffed at, think Japan's problem, but X10 for China's population is ten times larger.
China's military is the 3rd strongest. (globalfirepower.com) In general, the more money you have to spend on military, the better it will get; and coupled with China's (huge ass) population there is much potential for it's military.
The only ways I can see it NOT become a superpower is;
If the entire world shut their doors to Chinese trade. (Very unlikely, Western CEOs like to make money, and the world likes goods)
Chinese unrest inside the country (also very unlikely, Chinese people like to make money, and to go from living in dirt floor houses to soaring glass skycrapers...)
Wars (possibly the second most "viable" possibility. Though still very unlikely at that, EVERYONE likes to make money, and any war with China leads to the nuclear option)
Or, death by old people through massive spending on pensions and social services; and lack of workers. (The Communist party repealed the one-child policy, so it's up to the Chinese themselves to save themselves from old persons.)
Debate with me.