Someone I know is in Japan right now. He goes to a school of over 1000 people with 4 English teachers. Of that school, one person other than him speak English.
The Western world != The world.
If any language should be the world's primary tongue, it should be Mandarin Chinese. English isn't even clearly second, it's a toss up with Spanish and Arabic.
Anyway, creating a mandatory primary tongue will only serve to cause extinction for many tongues now still spoken - that is an undeniable fact.
And then, in a few centuries, scientists will scold us because due to this bad decision. We've lost an incredible amount of history and information. There are still many secrets held by history, and our supposed level of progress can still be contested because of it.
Cultural heritage is extremely important - too much of it has been lost already - and language is the most vital part of that. I do not deny that a global tongue may facilitate much... But it should forever remain a choice.
