A peek through the downloadable content menu in Alan Wake reveals a listing for the game's second, as yet unannounced episode, "The Writer."
"Our second downloadable content pack, 'The Writer,' finds Wake in strange circumstances; now fully aware of the thing that opposes him, he must survive one increasingly nightmarish situation after another."
The chapter will cost 800 Microsoft points. It says "67 days left" but that would peg this DLC's release to July 27, which is when the first episode, "The Signal" is known to release.
Second Alan Wake DLC Called 'The Writer' [Hell Descent]