Without giving any details away, Alan Wake and its DLC episodes left the game wide open for a sequel. It was almost like a season of Lost, where nothing is completely explained or resolved by the end. Naturally, fans are expecting a sequel, but although Alan Wake was critically successful, it didn't see strong sales compared to other major AAA games.
Thanks to LinkedIn and the ability to take a screen capture, however, we have confirmation that at least some work is being done on an Alan Wake sequel. An artist working with Halon Entertainment listed "In-Game Cinematic" work on Alan Wake 2 in April 2011 on their LinkedIn page. Since this news broke, the item has been removed, but a copy was saved at the source link below.
The original game was in development for over 5 years, but since much of that was fleshing out the game mechanics, I'm expecting that development on the sequel will move along more quickly. Let's hope Remedy releases more information during this year's E3 Expo. [Thanks DToid]