Just been officially announced including a teaser trailer - no actual gameplay footage.
This is a prequel set before GoW1 - an origin story before he became the Ghost of Sparta most likely dealing with events leading up to Kratos deal with Ares and other events around that time which have been touched on briefly in the other games. So no GoW4 as such - at least they haven't tried to write themselves around GoW3s ending. Plus now all the Gods can feature again.
Looking forward to this I know they haven't changed all that much from game to game but that's what I like - I like the gameplay (QTE excluded) and that's what I want more of. I know the trailer shows Kratos getting the Blades of Chaos but it looks like he may not have them to start which could be interesting and he more than likely won't be a pale ashen colour given the events that lead to that haven't happened yet (but could feature I guess).
What will he battle he obviously can't kill any of the Gods or Titans perhaps a battle with the pre-death Alrik, the Barbarian King. The Quest for Ambrosia sounds like it would make an interesting part of the game and Gyges and Asclepius may feature as a result. This is all pure speculation on my part based on the GoW comics.
More info and trailer here (trailer requires age verification)