With the Korean and English servers now Free-to-Play, the latest regional server to join the group is from Taiwan. From what I see, the Free-to-Play server will be a brand new one, while no announcements have been made for the current subscription server.
Going F2P on 24th July, it leaves just the Japan version of TERA as the P2P version, as it seems the model is still working well there for several games, including NCsoft’s. TERA China will be officially announced later this month as well, which will make 2013 a pretty good year for developers Bluehole Studio.