Yeah, it's looking almost certain that Sony's big, upcoming PS3 announcement will indeed be a new God of War title. Especially since there's already an Amazon listing for the thing. And a trailer.
A product page on Amazon, complete with box art and trailer (above), reveals the game is called God of War: Ascension. Interestingly, it doesn't seem to use the letters "IV" anywhere, and going by the narration in the short trailer it appears this is going to be a prequel.
The short trailer, which contains no gameplay footage, shows a stylised Kratos struggling against what look like his inner demons. Or hey, maybe outer demons! It also mentions that, before he was a God capable of killing everything, he used to be a man. Who fought not for rage.
The game's listing says:
Join Kratos as he seeks freedom, redemption, and the clarity to avenge his family in the most ambitious God of War adventure in the series so far.
Sony later confirmed the trailer via its Facebook page.