The very telling evidence is accurate: Aliens: Colonial Marines will be supported by Gearbox Software with enough post-release content to merit a Season Pass (via Sega Blog). The $30 token will be good for four content packs in all, with the first one -- Bug Hunt -- coming in March 2013. The Season Pass will be available for PlayStation 3, Xbox 360, and PC; no mention of Wii U.
Bug Hunt is a Horde-like co-op mode that plays out on three mode-specific maps. There isn't any mention of player count for this mode, but expect it to be four based on the way campaign and the No Escape co-op mode work. Three additional DLC packs will follow Bug Hunt, with the final one to be released by or before August 2013.