It is all about "what language do I need to learn to have a good income". The difficulty of language matters little, as long as speaking the language badly is s

It is all about "what language do I need to learn to have a good income". The difficulty of language matters little, as long as speaking the language badly is still more profitable than not speaking it at all. That is partially about economic power (if your country offers many good jobs, people near you have an incentive to learn your language), and partially about military power (if you can make another country speak your language at gunpoint, at least in government-related jobs, their economical power becomes another argument for learning your language). Therefore the popularity of Chinese will depend on how easy it will be for people who learn Chinese to increase their income. Compared with the expected increase of income from learning English. Argument "but most important people in China speak English anyway" is less relevant if learning Chinese provides you even better advantage from cooperating with them. For example, most people in Germany speak English, but I suppose that being fluent in German still makes it easier to find a job in Germany.