For those of you that care, The next "Wake" game is neither a sequal or DLC. There keeping it under wraps right now but remedy said that they will realese more info when the games anouncement trailer is realesed.
Heres the article from joystiq as well as the FULL STATEMENT FROM REMEDY.
http://www.joystiq.com/2011/05/10/new-alan-wake-confirmed-but-its-not-alan-wake-2/