Anyway, Square Enix had a Final Fantasy XI event today, in which the very definition of what Final Fantasy XI is changed somewhat. Most importantly, the final additional scenario to the game was announced; called "Rhapsodies of Vana'diel," the scenario will come in three parts and are intended to incorporate aspects of the game's history into new battles and loot in an effort to create a feeling of closure to the adventure. These three pieces will be free to all players.
The three pieces of "Rhapsodies" will be released in May, August, and November 2015. In March 2016, the game will be shut down for Playstation 2 and Xbox 360 players, which seems like it might be well due. This will leave only the PC version as an active platform. Sometime before the March shutoff, as well, the game managers are planning a final gameplay event called "The Goddess' Gala," which promises fun content for both active and lapsed players.
While the ancient platforms are being eliminated, though, a new platform is being announced; Final Fantasy XI mobile is in the works now for smartphones and tablets worldwide. The game will carry the XI name, and has optimizations intended to make the game more playable via touch; however, it is not yet clear if it will interact with the existing platform or will exist solely on its own servers and will be multiplayer only with other mobile players.
Also announced today, for release in Japan later this year, is a mobile game set in the universe and leveraging the characters of Final Fantasy XI. The game is called Final Fantasy Grandmasters, and while it will have ad hoc multiplayer, it's not to MMO scale and the gameplay based on screenshots looks like a hybrid between MMO combat and more standard Final Fantasy line-up-and-sword-them fighting. It's aiming for beta sometime in April, but again, there's no release planned outside of Japan.
Source: Gematsu
Updated the post to reflect that.