User blog comment:Master Sima Yi/Assassinews 03-03-'13 — Assassin's Creed IV: Black Flag trailer and screenshots/@comment-1379990-20130303192139/@comment-1153722-20130303193530

Well, they aren't really major spoilers specific to the game. You'll see.

And they wouldn't do that for a main game, especially not after the plot points they introduced at the end of AC3.