Announced in this morning's Letter From The Producer, Revenge of the Horde—yes, Horde—is Final Fantasy 14 (opens in new tab)'s next major patch.
Details are scarce, but patch 3.3's defining feature is the 'Deep Dungeon'. Players start at level one, scrabbling for items within the dungeon itself to progress. This sort of thing is more usually seen in FPS and MOBAs. Some Final Fantasy trimming could suit it.
In addition, a raid finder is coming, the Dragonsong War will conclude, beast tribe quests get Moogles and dragons involved, and the Anima weapons series (opens in new tab) continues. Scraps of information are set out on the official forums (opens in new tab), or you can watch the stream (opens in new tab) for yourself provided your Japanese is on point.
Reaction to Revenge of the Horde has been uncertain, with the best response coming from none other than Blizzard:
.@FF_XIV_EN Revenge of the... what? pic.twitter.com/W1MmQtbwvsApril 29, 2016