User blog comment:Master Sima Yi/Assassinews 03-03-'13 — Assassin's Creed IV: Black Flag trailer and screenshots/@comment-1153722-20130316111448/@comment-186.153.252.203-20130317004956

That da Vinci sketch is from a hidden blade as well as the Apple, so I'm assuming that will have to do with the "Pieces of Eden" side of the story.