This would not work, the game would have to be completely redesigned from the ground up. Which would probably include a new game engine too. The game would probably have to go down like it did for 1.0 when releasing 2.0. I don't think any mmo has ever been changed from one form to another. An mmo is usually designed to be either tab target or real time and cannot be switch from one to another.

Maybe the next Final Fantasy mmo will be real time. If they release another one that is, so maybe another 10 years from now?