I have not played this yet, seeing as my PS2 is hooked up to the Plasma and vying for time with both the 360 AND "Dancing with the Stars" (Thanks hon
), but it looks to be quite outstanding and I may need to get it once the hype dies down a bit ($$$).
As for "what's next", I think they are stuck. I can't see how they would be able to have Kratos as the lead in the next one. If anything, it would probably be a relative (a son? You know he got bizzy).
Maybe the next would take on the role of the sappy hero trying to fix all the damage he did while a LOT of angry gods still throw stuff at him in rememberance of his line.
Hard things to mix with it would be additional RPG elements, or Co-op. But having an all out smash-brothers like carnage contest might be an interesting extra that would give the story-line game a second life.