I ran across this article today... Indo-Anglians: The newest and fastest-growing caste in India It's about the rise of English speaking households in India. Particularly for a country like India with multiple languages and castes, English serves as a uniter across castes, and many of these households are speaking English as their primary language. It appears to me that there has not been a more internationally used language since Latin. I suspect that by the end of the 21st Century more people worldwide as a percentage of the population will be able to speak English than currently, even with the relative decline of the Anglosphere nations.
I suppose because of the successes of the USA, and those around the world who wish to share in these successes, those outside of the USA found it necessary to speak English. Going back 40-50 years, I suspect any foreign nation who mandated English as their primary language in their education system, today are reaping the financial and cultural benefits. At least in the business world speaking English to do business with Americans allowed outsiders quick access to our economy...
English is also easy to use spelling and grammar really don't matter anymore, emoji help and only a basic proficiency is enough to get by. I English #1 language. C how EZ dat wurks.
About 20% of the world's population speaks English...but only about 4% speak English as their first language. More people speak Chinese and Spanish than they do English. If the US didn't have our economic successes, being a world economic powerhouse, I doubt English would become the dominant language...
I wonder if as the U.S. loses international prominence, English might someday begin receding from it's position as the global language. This has happened to other languages in the past. Look at the long linguistic history of the Middle East. Akkadian, Aramaic, Persian, and Greek used to at one time or another be the uniting language across this region.
That may happen, but there needs to be another language to replace it. I don't think it will be Mandarin.
What would probably have to happen is in the distant future other countries would have to become weak enough, and then some other country would start conquering a region of the world becoming an empire. At that point it might become the most dominant nation-state in existence, and by extension its language. Suppose for example the US defaulted on its debt, suffered severe economic issues at home, and could no longer afford to maintain its military presence around the world. A decline somewhat akin to what happened with the British Empire.
Esperanto is humankind's sense of humour, since we already have English. No one takes Esperanto seriously because of English, and that's the joke.
The difference is that we've had two back to back English speaking great powers. Indians became adept at English not because of America but because of Great Britain. Now of course, Britain isn't the reason that India still excels at English (over 100 million Indians speak English), America is now. That back to back great power combo using the same (more or less) language have set the importance of English up, I think regardless of what happens to the US. If the US collapses this century and China rises as the worlds major economic power, that still doesn't mean everyone will be watching Chinese movies in Mandarin or other cultural influences. English may outlast the US in importance.
Machine language...probably a derivative of English and combined with graphics and math can be developed for written language. The bigger challenge will be a universal spoken language...
My point was that if something happened internationally and English no longer was the global prominent language, it wouldn't be difficult for India to go back and mostly ditch the language. This could happen over only one or two generations. The BBC had an article about this: English or Hinglish - which will India choose? The main reason Indians are trying to learn English right now is the market opportunities in other wealthier countries. Do you remember the late 80s? There were a lot of American businessmen trying to learn Japanese. What ever happened to that? It was a bit of a fad, because Japan only held a prominent position in American trade and business for a short time.
English is easier to use than Chinese now Spanish is easier to use but still not as adept as ease of use like I pointed out some emojis and some creative use of letters and numbers you can get a point across. English EZ2 Use. C EZ (try that in Chinese)
Seems there are a couple of variables; First, the quantity of people currently speaking certain languages, and second, being able to communicate to drive economies. We know more people speak Mandarin and Spanish but as you say Mandarin might be too difficult to force on everyone. Economically, 40-50% of the world's GDP is created by English speaking nations, certainly including the USA, so this makes English the best bet. Will these trends change over time and encourage a move away from English...we don't know...