User blog comment:Master Sima Yi/Assassinews 03-03-'13 — Assassin's Creed IV: Black Flag trailer and screenshots/@comment-4999424-20130322171533
Some Assassin's Creed 4: Black Flag PAX East photos(no demo or in-game).
From Article:
McDevitt and Ubisoft refused to comment on the involvement of character Haytham Kenway(Side note: they did the same with Cross) in Assassin's Creed 4. Haytham a primary character (and antagonist) in Assassin's Creed 3, as well as a fan-favorite addition to the series. Since Edward is Haytham's father, there's been some speculation at Game Front that Assassi's Creed 4 may really be about Haytham(Side note: maybe not about, but involve in a way), since he's a character who left the Assassins and joined their arch-nemeses, the Templars(Side note: we know how he changed side). Hopefully we'll have more information on the Haytham front in the future, but for now, Ubisoft isn't talking about him.