[samus]

I disagree. There is no possible benefit to a monoculture of language that would justify the immense loss of culture and of different ways to see the world.

Cultural spheres have always managed to come up with a lingua franca that enabled them to exchange ideas. English fills that role currently and will probably endure to dominate. Even if something goes monumentally wrong with the Anglosphere, it will endure until another language manages to step up to that role.

Children are perfectly able to learn multiple languages within a few years by pure immersion. I can't see what further optimization here would achieve.

Still, judging by the events of the past, languages that are not sanctioned by some state will probably all die out by the end of this century. Further erosion is very unlikely though. The language of any country with at least, say, 50 millions speakers is probably safe.