Ok, fun hypothetical time!
Let's say for some reason, let's save some time and just say space magic, you can now pick what language everyone on Earth will speak for the rest of history. You get to pick what Earth's universal language is.
So what do you pick? Any language can be used, including dead languages and fictional ones.
Note: All the other languages will still have existed, and can still be learned. So you can still learn how to speak *insert your native language*, you'd just learn it as a second one.
Let's say for some reason, let's save some time and just say space magic, you can now pick what language everyone on Earth will speak for the rest of history. You get to pick what Earth's universal language is.
So what do you pick? Any language can be used, including dead languages and fictional ones.
Note: All the other languages will still have existed, and can still be learned. So you can still learn how to speak *insert your native language*, you'd just learn it as a second one.