Isn't language loss a good thing, because fewer languages mean easier communication among the world's people? Perhaps, but it's a bad thing in other respects. Languages differ in structure and vocabulary, in how they express causation and feelings and personal responsibility, hence in how they shape our thoughts. There's no single purpose "best" language; instead, different languages are better suited for different purposes. For instance, it may not have been an accident that Plato and Aristotle wrote in Greek, while Kant wrote in German. The grammatical particles of those two languages, plus their ease in forming compound words, may have helped make them the preeminent languages of western philosophy. Another example, familiar to all of us who studied Latin, is that highly inflected languages (ones in which word endings suffice to indicate sentence structure) can use variations of word order to convey nuances impossible with English. Our English word order is severely constrained by having to serve as the main clue to sentence structure. If English becomes a world language, that won't be because English was necessarily the best language for diplomacy.
Jared Diamond, The Third Chimpanzee: The Evolution and Future of the Human Animal
expression, language, thought