This picture, which appears to be for Assassin's Creed III, leaked today. Allegedly, this comes from the Best Buy's internal employee news, who emailed Kotaku with this possible art. Apparently, another picture was sent to them, which they have not revealed, saying that Ubisoft will be unveiling the game on March 5, and that there'll be pre-order bonuses.
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If this picture happens to be legitimate, it appears that the third game in the series would be set in the American Revolution, as rumored before. In the background of the picture you can see the original Continental flag, the Assassin wearing an 18th-century military jacket, his weaponry, jewellery etc.
UPDATE: Thanks to
Game Rant, we have our first look at the official PS3 Art and two other covers from Gameinformer for the game.