Still, with little more than the titles to go from, a certain amount of informed speculation can be made about the nature of these add-ons. A quick Wikipedia search reveals that the Battle of Forli was an actual historical event that occurred in the same region that Assassin's Creed II takes place, though with it dated in 1282 AD, it precedes Ezio's story by several hundred years. Similarly, before it was a bad Bruce Willis movie, the Bonfire of the Vanities was a literal bonfire of items deemed to be sinful during a period of religious fervor, though its occurrence in Florence, Italy circa 1497 puts it smack dab in the middle of Assassin's Creed II's story. This all seems to keep with the tone of Assassin's Creed II, which routinely injected its own fictional tale of Templars and Assassins with people and events ripped from the pages of history.
With Assassin's Creed II still fresh in my mind, I'm actually pretty eager to have another excuse to return to its richly realized world and learn more about the grand conspiracies that drive it. And of course, to stab more dudes in the face.
UPDATE: Ubisoft PR says to expect more details about these DLC packs later this month. Also, as many of you have pointed out in the comments, it seems likely that this stuff will slot into the blank chapters that the main story in Assassin's Creed II skips over.