According to recent company trademarks, it looks like Square Enix is set to announce a brand new expansion pack for the long-running Final Fantasy XI that may be called "Seekers of Adoulin". For those unfamiliar to the lore of Vana'diel, Adoulin is basically the source of a lot of information for the world and through its tremendous library is said to contain more knowledge than Windurst, the magic capital, and lies to the far West of the Middle Lands continents. Up to this point, it was only spoken of through character dialogue and wasn't accessable.
There isn't really information to go on since we're only talking about trademarks, but with the annual VanaFest happening tomorrow, except a big reveal along with further plans for the long-running game. Once it is released, it will be the fifth major expansion for the title after Rise of the Zilart, Chains of Promathia, Treasures of Aht Urhgan, and Wings of the Goddess.
Final Fantasy XI recently celebrated its 10th anniversary and will also be having its own concert in celebration. We'll report on whatever big news comes out of VanaFest 2012, a big fan-focused event dedicated solely to the still-popular MMO.