God of War IV’s score may be from Timothy Williams who worked on Conan the Barbarian (the 2011 film), Rise of the Argonauts, and DOTA2. You can listen to his work on Defense of the Ancients 2 here.
Williams lists God of War IV as one of his upcoming projects in his resume.
PSM magazine claims God of War IV will be released in mid-2012 and will have online multiplayer. Kratos will team up with his brother Demios who was introduced in God of War: Ghost of Sparta to escape the afterlife.