From the same press-release we found out that “Crysis Warhead will also come with Crysis WarsR, a tailor-made experience for multiplayer gamers, featuring three diverse match types and 21 maps.”
A few more details about Crysis and its feature can be found in this interview with Bernd Diemer – Crytek producer. For example, Crysis is a trilogy and “Warhead is not a sequel, this is a separate story, stand-alone. It’s not meant to conclude all the things in Crysis. It sort of fills into a couple of blanks in the original story, but it’s not Crysis 2 or Crysis 1.5.”