"Every language" sounds like a massive stretch. Then again I come from a country of 200+ different languages, so maybe my expectations are a tad higher than most. Unfortunately, given the reliance on machine translations, I don't expect it to be a useful learning tool for most of those languages any time soon. As an aside I'm curious about your voices, especially for highly tonal languages like Yoruba that also don't…
It's a good point about the "every language" part. That's really the goal of the project - we've been adding about 20 languages a month since we started, and don't plan to stop until we support every language. However we're not there yet, give us a few more months to live up to that ;)
We have some ideas for languages that don't have widely available TTS, but we're not ready to share anything quite yet.