The first thing to clear up about Crysis: Warhead though are the technical details of its existence – is Warhead an expansion pack, or a straight up sequel to the original game? Will it require the original or is it standalone?
Well, let's take it from the top. EA and Crytek are actually billing Warhead as neither an expansion or a sequel to the original game, responding even to direct questions about the matter with the here-nor-there reply of "This is the latest instalment, not a sequel or an expansion." In other words, though Crysis was announced as a trilogy, this second game is not the second game in the series.