It seems these days that language-oriented models are commonly becoming multilingual by default. There are a lot of common threads when understanding sentence construction between different languages. French and English have different rules but they will still have things like nouns, adjectives, subjects, prepositions, etc. It seems that by training models on many languages you get both a more robust understanding of language, and it saves you the trouble of having to make many more localized models for every language. I also believe that the other languages help the models construct sentences in languages which have very small training sets. If it has a few examples in a rare language as well as good translations to a better-known language, then it can provide good support for the rare language.

We also see in image generation models that multi-modal networks are more powerful than single purpose networks. As we move towards more advanced AI systems I suspect we will see more and more generalizable networks with distinct advantages over separate networks that get plugged together.