While we don't have any screens or official word from even Ubisoft, GameStop seems content to sell us the rumored single-player DLC, so long as we want to preorder from the game retailer.
In an e-mail sent out to customers today, GameStop revealed that they have opened preorders for Assassin's Creed: Revelations: Lost Archive, a downloadable content pack that will be made available on February 28th. The pack is priced at $14.99 and will be available through GameStop for Xbox 360 and PS3.
We're following up with Ubisoft on these details, but it seems certain that single-player DLC will be available later this month. Maybe Ezio isn't quite as retired as we thought.