This I read in the GameInformer magazine. They interviewed Stig Asmussen and asked a some questions but like this one.
During the course of the game, Kratos takes down all the major players but not the entire pantheon. Where there any gods that you wanted to include but didn't make the cut for the final game?
"No. This is the cast that I wanted to see. We needed time to build a small amount of backstory between Kratos and the gods he would eventually take out, and these were the one that made more sense. These are also the guys that we saw at the end of God of War II."
So there you go he had no plans on adding anymore gods, I guess that answers our questions of the missing gods. But hopefully in Ghost of Sparta we'll see what happened to them or maybe in future games.