Twitter user Shinobi602, and a website belonging to former Sony artist, Finnian Macmannus, have both leaked information and images suggesting the next God of War game is to be based on Norse mythology. Sony itself has not revealed a GoW4 as of yet, and specific images and sites related to the leak have since been removed.
The images depict a figure resembling Kratos in different Norse mythology-inspired settings. The leaked images are available on NeoGAF, and there are quite a few of them. In addition, Kratos is mentioned by name in some of the concept drawings.