At Vanafest 2010 in Tokyo, Hiromichi Tanaka, the lead developer of Final Fantasy XI, announced that game will get three new high level battle area additions this year: Vision of Abyssea, Scars of Abyssea, and Heroes of Abyssea.
Vision of Abyssea will be the first release, this summer. The other two are not yet dated. All will cost $US9.99 and will require the previous expansion packs Wings of the Goddess and Rise of the Zilart.
[thanks to Stephen for the heads-up]