Personally, I'm very much looking forward to using a speech model like OpenAI's advanced voice mode to learn language. It can already do things like speak quickly or slowly which traditional TTS systems can't. Also, in theory a speech model could tell me if my pronunciation is accurate. It could correct me by repeating my incorrect pronunciation and then providing the correct pronunciation. I don't actually know how capable OpenAI's advanced voice mode is in this regard because I haven't seen anyone actually test this but I'm extremely curious to try it myself. If other voice models can achieve this then it will be an incredible tool for language learning.