Yesterday, the French website GameBlog reported a number of details surrounding Comet and its story. A Redditor named GalakFyarr translated the article here. (Kotaku's Evan Narcisse used his French skills to verify GalakFyarr's translation, which looks about right.)
GameBlog's report claims that Comet will take place in and around 1758; that it will star a sailor named Shay who betrays the captain of his ship; and that it's set on the Atlantic Ocean. Comet, GameBlog says, will continue the nautical theme established in last year's Assassin's Creed IV: Black Flag.
We haven't been able to confirm all of those plot details, and some of it appears to be speculation by GameBlog. But people familiar with Comet tell us that this fall's last-gen Assassin's Creed will indeed be set in North America and star a protagonist named Shay, who is a member of the Templars, the assassin-hating order that has traditionally served as primary antagonist in the Assassin's Creed games.
We also hear that Comet will let you go to New York and do a great deal of sailing along the coast of the Atlantic Ocean. One source describes the game as a cross between Assassin's Creed III and the Freedom Cry DLC for Assassin's Creed IV. Sources also say that Haytham Kenway and Adewalé will make appearances, among other returning AC characters.
(Haytham, fans will remember, was the surprise character who players controlled in the early hours of Assassin's Creed III before assuming control of the lead character, the assassin Connor, Haytham's son. Haytham is himself the son of ACIV protagonist Edward Kenway, whose first mate, Adewalé, would eventually become an assassin himself. Haytham, notably, was a Templar.)
So it sounds like Assassin's Creed Comet (this is the game being released on the Xbox 360 and PlayStation 3; Unity is for the Xbox One, PS4, and PC) will be set in the same era as Assassin's Creed III and IV: Black Flag; it notably seems to continue the nautical theme, and seems to have the same characters and story arc. Depending on how good it turns out, it might actually be worth it to get both the major Assassin's Creed releases this year. The playing as a Templar part sounds intriguing to me too. Still, Unity takes precedence, if I have to pick.