The IMF predicts that China's economy will overtake the US in some ways in 2016. There is lots of room for debate about how the figures are interpreted (some of the debate even takes place in the article). With a billion more consumers than the US has I see it as inevitable that the Chinese economy will grow to be larger than the US, at least in terms of GDP. The question is what the effect will be in either country or in the rest of the world.
http://www.cnn.com/2011/BUSINESS/04/...ex.html?hpt=C2