Part of the problem with social media is getting noticed/finding community (at least on X). Maybe if the AI finds you interesting enough it could help broker connections to other people... I can't tell if this would be weird and terrible or if it would be nice.
I could believe it supplements, but I do not think mediated communications will replace.
I could believe it does autotranslate on the fly. I would enjoy having more nuanced conversations with people in economies where their ESL is low and I do not speak their native language.
Only the AI would see what you say though. It may or may not tell some other people it chats with about it. And even then, it probably won't quote you word for word.