As I said, this game will be multiplayer. You'll be playing in large scale wars with Kratos as the General. You'll be able to create your own Spartan warrior and play with friends; customizable skins, tattoos, armor, weapons etc. The main campaign will be up to 4 player co-op. You'll play through several battles against various races with some mythological monsters thrown in. The ante will go up after you make your deal with Ares and gain more abilities. You will serve Ares while slaughtering thousands. You will then be betrayed and kill your family, turning you against Ares. There will be a battle between you and Ares at the end and you will actually have the upperhand but because of a trick from the Gods, Ares will escape your wrath.
Then the multiplayer. It will be 16 players. You'll be able to play as Spartans, Barbarians, Arcadians, Persians, Athenians etc. There will be a few match types, 8 v 8 team death match, survival mode, and free for all. You will get to customize your character or choose from a list of characters including Zues Ares, Athena, Posiden, Hermes, Helios, etc.
This will be the most gritty GOW game. Expect much more blood and expect to be vunerable to injury that effects your performance. Also expect the ability to pick up dropped weapons or be able to steal weapons from your enemies. Customization will be huge in this game. Expect new comrades for Kratos as well.
A nightmare.