The Economist seems to have a couple articles that talks up the idea of China taking over the world as China recently surpassed Japan as the world's second largest economy in nominal terms. One of the articles suggests that China is by many measures the world's largest economy, such as by annual sales of passenger cars, and alludes to a time when the British Empire was in relative decline. But, I might suggest that this is a bit of a stretch. The British Empire, before the aggregate size of its economy was overtaken, was already being surpassed by the United States in industrial technology and Germany was pioneering a brand new industry, petrochemicals.
We no longer live in a world where countries are compared by its annual pig-iron output or by railway mileage. It's easy to acquire, mimic, and improve upon already existing technologies, but for a country to drive innovation is not easy. France, with its blotched Internet initiative and Japan with its blotched supercomputer initiative come to mind here. In the 21st century, I would like to suggest that the technological gap between the West and China/India is so vast that such comparisons may not be directly applicable. If the developed world were ever to engage in a land war with China somehow, then I believe the comparisons might be a bit more substantive in its content.
Disclaimer: This post is of course a very American-centric view. If I were to say live on the Korean Peninsula or live in a country that borders China, or even on one of the islands that naturally encircle China, then China's astronomical rise in industrial output matched by astronomical rises in military spending, then my perspective may be not be as relaxed.