But I agree that it's not a given that China will be the superpower, and even if gets there, it's not clear that Mandarin will immediately become that important.
Sure, you've got user manuals in multiple languages, but for chip specification, pin diagrams or anything really, I am unable to find manuals in a non-English language. I believe, the same thing applies to other Engineering fields too. Sure, you've got formulae that's universal. Say, you're a Mechanical Engineer working on some modeling-simulation software, you'd be hard pressed to find a non-English version.
And seeing that most of the world is embracing technology, even in the smallest capacity, I feel English isn't going anywhere.
Over the past 150 years this past generation is the only one not to suffer some horrific war, genocide or starvation. China has a revolt somewhere almost daily, it has none of the institutions we are pretty sure are necessary to managing power (independent judiciary, enforceable contracts etc) and has worrying signs of becoming a mafia state, with none of the benefits of one guy in charge ala Putin .
So basically there are a huge number of ways it can go wrong, very little to hold it together except the fear that if we don't keep on this course it will be a lot worse.
Chinese people are learning English, they are already better at it than the Japanese. But again, huge population, many of the powerful guys don't feel like learning or speaking English for face reasons.
Totally agree with you on language choice, learned Japanese in the 90s, never went anywhere with it. Mandarin has been much more rewarding. Take it from me, an American living in china.
Much like you, I studied another language before I found one that worked for me. I studied German, before I committed to Japanese. I had fun studying it, but I was never excited enough to the point where I wanted to move to Germany. Learning a language is a very difficult process (especially Chinese for English speakers) and having the freedom to choose to take a different language is what allowed me to find one that I was truly passionate about.
I believe that Chinese will continue to remain important, but forcing kids into it might dissuade them from finding a foreign language they truly enjoy. That's all I wanted to say.
I have strong doubts that Chinese will ever become the lingua franca of business. It has language features that make it difficult for us Westerners to learn (mainly, tones that carry semantic meaning)... I think that Chinese people will be more motivated to learn English instead.
Also, who's to say China's economy won't crash and burn in the next 50 years? Forcing Mandarin on everyone is putting all your eggs in one basket. Learning a foreign language is a difficult thing, and one good way to keep motivated is to be truly interested in the culture of the country whose language you're studying. I'm all for mandatory foreign language education, but I think people should be able to choose a language they care about. They shouldn't have to take Chinese because it might be a big deal in the future. Learning any foreign language can open doors, not just Chinese. Take it from me, an American living in Japan.