Regardless of what the world might think China is growing faster and faster. The U.S is still powerful but it is clearly starting to struggle a bit. At the moment the U.S is the only major super power but that can change. That is not to say that there will be a war or anything and they may coexist as super powers for along time. Despite heavy criticism and clear mistreatment of there people the have clear intentions to be a dominate power and the U.S know this. While it is not certain that China will replace the U.S, what is certain is no superpower lasts forever. One day, sadly, the U.S will not be dominate (it may not even exist in the future), history has shown this time and again.
The United States is recognized as a superpower not only because of their wealth and military power, but because they are known to be a leader in world affairs. I don't see China ever taking that spot. There are already questions about their economy and leadership. Their communist regime will deter other countries from them as well.
China has certainly changed since the days of the "Shang Dynasty, but to compete with the likes of America it needs to do more than grow it's expanding infrastructure. For example, we need to see a more 'developed' culture, especially around the topic of human relations. Instead of the basking in the glory of Tiananmen Square, maybe they should take a more dignified approach and show a little more compassion to all it's people. Only then should they be considered a superpower. It's just my opinion.