Earlier this year, an image for a project called "Assassin's Creed: Rising Phoenix" was uncovered, which Ubisoft promptly denied involvement in. Many speculated that this was a PlayStation Vita game with a release date of October 10th, but considering that date came and went, nothing really came out of it -- until one gamer uncovered a hidden image in Assassin's Creed IV with the same exact logo font.
If this is real (and not a joke by Ubisoft), it could be anything. Perhaps it's another animated tie-in short like Embers, or a side-story for the Vita like Liberation. Now that I've played through Black Flag, I can see clearly now that the area is supposed to be a lower level of the new Abstergo Entertainment facility, so it's also possible that it will tie-in Assassin's Creed IV and the inevitable V in some way through a modern era story.