The publisher has released the game's official box art along with the statement: "We confirm that Ubisoft will announce all the details of Assassin's Creed IV Black Flag on Monday March 4th at 5pm GMT."
According to various leaks this week Black Flag is set during 1715 in the Caribbean, with Jamaica, Cuba and the Bahamas among the islands that will be visited.
Ubisoft has confirmed Xbox 360, PlayStation 3, Wii U and PC as platforms for the game. The PS3 version will receive "60 minutes of exclusive gameplay," it's said.
[UPDATE: Ubisoft's website has seemingly confirmed the Assassin's Creed 4 release date as October 29, 2013, with versions also set for "next-gen consoles".]
Earlier this month Ubisoft confirmed plans to publish the new Assassin's Creed game during the financial year ending March 31, 2014.