If somebody wants to do that they may, but it won't officially be part of this site or anything (in other words, I'm not doing it, and I'm not hosting it). There will probably be rp rooms in the chatroom eventually, but I know it won't be quite like a MU*.
I used to be itnerested in starting a MUCK a long while ago (Disney's Aladdin-based) but I couldn't get together enough people who knew how to actually program one, so obviously I was never ale to do it.
I like MUCKs and MUSHes.