The original Crysis was expanded with Warhead, allowing players to follow Psycho as he was separated from Prophet and the main protagonist, Nomad. With the announcement of Crysis Remastered, some rumours suggested it would include Warhead, and perhaps even a sequel, but Crytek has now apparently shot all those rumours down.
According to Inverse, a Crytek representative reached out to them with a simple, but clear, statement: "It won't include Warhead or any of the other games from the series."
So there you have it, Crysis Remastered will only include the base game's single-player campaign, without the expansion, or the original's multiplayer features.