User blog comment:Abelzorus Prime/Could Shay be a Kenway?/@comment-6517-20140704190556/@comment-27202257-20140705221700

After following the sources from that article to the origin of the information gets you to this reddit page, where they translate the French source as follows:

"While writing this dossier, the name of a second game being developed alongside AC:U hadn't leaked yet. It has now, and the name is "Comet", another leak from the NeoGaf Forums, on which we have found other leaked details about Project Comet, just like what happened with Unity.  AC:C could take place ca. 1758, on the Atlantic Ocean and form a sequel to Assassin's Creed: Black Flag and its maritime context. The player would take control of a joung English man called Shay, who would betray the captain of his ship, an old man called... Adewalé! It would be a shame not to profit from the engine developed by Ubi Shanghai and its breakthroughs in maritime simulations.  AC:C would then continue the 'piratey' Assassin's Creed, in continuity of AC4:BF and AC4:FC, which would explain the stand-alone status of the AC4 DLC.  We could potentially be having 'Black Flag 2', in short."

Sounds like a boatload of speculation to me.