I don't think Kratos will be the center of attention in this next one. I think it'll be a different character.
God of War is fun, just pure fun, and it isn't trying to be anything but it's own franchise with it's own uniqueness.
Now, Athena is still alive. Whatever plan she has for that world could still be great enough to warrant an entire game of Kratos being the world's savior. I'd think, with little effort on my part, that Athena would send Kratos around the world to retrieve, protect, and unseal powerful elements to return balance. With this being said, they could create new gods or use previous less important characters as power hungry mortals trying to replace previous gods.
I hope they choose a new character with Kratos becoming a secret boss inside of a ruined Mount Olympus. Oh well, after seeing Uncharted 4 slated for 2015, God of War 5 and Gran Turismo would indeed make huge splashes for 2016.