I doubt there will ever be an official RP server as much as I doubt RPers would transfer to it if one was made, simply because the activity on that server would be the same as in a server with mixed RPers and non-RPers such as Balmung, where I am, and Gilgamesh. As a roleplayer and co-leader of an RP linkshell, I have observed my members and others, and I assure you, there is only a very small percentage that will invest on roleplaying most of their in-game time.

Most of roleplayers spend their time doing endgame as much as non-roleplayers, and will RP only during breaks in a tavern, or when an event is scheduled by the Roleplaying Community. In the end we're just like non-RPers, and even though we may not share the same reasons to do endgame (looking for good-looking gear rather than high stats), the goal is the same. 90% of players will go after the latest content, be it a roleplayer or a non-roleplayer.

Of course there are people like me who really only like to roleplay and only progress the game when they're bored, but we'll never be enough to fill a server. Most of RPers will want to stay where there's non-RPers to be found, so there's always a good number of participants to endgame.