Just last week, the latest PlayStation 4K rumor mentioned GOW4, which everyone believed was God of War 4. Yesterday afternoon, now defunct website NerdLeaks posted several pieces of concept art showing Kratos with a beard and an axe. The entire NerdLeaks website has gone offline since the initial posting, but not before NeoGAF users could salvage the work. The pieces originated from the personal website of someone who worked at Santa Monica Studio last year.
Multiple pieces mention Kratos by name and how the environment will interact with him, removing all doubt that anyone else could step up to become the protagonist. According to the images, the God of War icon will be visiting at least two of Norse mythology's Nine Worlds and will at least visit a prison. Industry insider shinobi602 mentioned God of War 4 and Valhalla in a tweet yesterday morning before NerdLeaks posted the concept art. Polygon has also received word from their sources that the pieces are legitimate, so there's a real possibility Kratos will be finding himself matched against Thor or even Odin.
Sony has declined to comment on the authenticity of the images, but that could simply mean they aren't ready to talk about a God of War 4 yet. Until Sony or Santa Monica Studio confirms or denies the existence of God of War 4, all we can do is speculate based on the images shown. If this turns out to be true, Alfheim, Vanaheimr, and who knows how many of the other Nine Worlds will be waiting the destruction of Kratos on his next journey.
Who is the god of war in Norse mythology though?
Odin? Tyr? Someone else?
In any case, I do not think that they wanted to take the risk of making a new protagonist.
Even the unnumbered games used Kratos as the protagonist.
There are quite a few series that handle Christianity's deity and other beings in main roles.
One in particular that I can think of is the Megami Tensei series.
Egyptian, African and Hindu deities would be nice to see in more prominent roles, though I'm not sure if God of War is where I'd like to see them...
Also, I think that Celtic(?) mythology would be cool.
The only thing I've seen about that where some of the characters from that were in somewhat more prominent roles was in the Fate/ series.
The article makes me think that they're going to go with the revenge thing again.
Kratos will probably get sent to Hel by Odin as a result of Loki transforming into someone else.
After he gets out of there (probably with help from Loki), he'll end up fighting Thor, Odin and the others until he realizes that Loki was the real cause of him being sent to Hel in the first place.