Regarding the existence of the next God of War, Amazon France has officially listed God of War IV for Playstation 3. No release date is given, however, a lot of rumors praise there seem to be the inclusion of online co-op on the next God of War.From what we heard ,we can expect it early 2013 release. However,Sony itself haven’t comment whether there will be a new God of War.

There is also a trailer tease which featuring someone,more like kratos brother
From what we can guess, it seem like someone is telling kratos to wake up

Brother.
The phoenix has-been drinking your blood, full of your anger, your strength, and During her rebirth, she Also has let you in life.
Now I ask you, what are you going to do … would you leave me here in hell?
Kratos, wake up, wake up!