Since I'm of the mind that China is a natural resource poor nation, similar to Japan, which has embarked on an unprecedented acquisition around the world of natural resources I don't believe they represent as big a threat as the Soviets.
I believe China's economy is built on false growth numbers which is made possible by their currency manipulation and huge trade imbalance. The Communist Chinese government needs America more than we need China. Cheap goods can be manufactured in other regions and as China changes, it will make manufacturing stateside attractive again. So I'm not sold on China's hegemony or global economic dominance.
However, that doesn't mean that the US can continue to propogate laws and regulations that detour American investment and manufacturing, which has occurred over the past 20 years.
America depends on energy as does every country. With cheap reliable energy there is no economy. The US has hundreds of years of oil. She has another couple hundred years of natural gas and another 300 to 400 years of coal. But yet the federal government place such restrictions on industry as to turn business away. We are a nation that is self reliant on energy and choose not control our own destiny.
So the answer to your question is 10 years or less if the US government continues its failing energy, business, and current economic policies. However, should the government remove the shackles from private business and entrepreneurs China will never over take the US.
America's destiny is in our own hands.