Many years ago there was a project in which researchers swapped localization strings to turn The Sims and Grim Fandango into language practice experiences. Generative dialog that is contextual and skill-appropriate dialog could also be a killer application for language practice.
This excites me. Everyone wants to learn a new language, no one wants to slog. But I'd pay money to play Grim Fandango, and get the chance to ask "What does Morte mean?" and have the LLM, in real-time, tutor me. And if I get bored, I can game on, business as usual.
But just give the AI a list of words I currently know, and it can slowly slip in more and more vocabulary, and maybe full sentences.
Duolingo has already gone all in on AI.