I do think they will find and portray god, cause the have portrayed other religions gods without problems, they even gathered all of them in one room, so why not god. But i do not think it is chuck, cause if it where chuck dean's necklace would have some point burn hot like Cas said it would in God's presence. I sure hope they find and portray God, hopefully in season 10!
It was confirmed after the end of season 5 that Chuck had been God (he must have blocked Dean's amulet from burning in his presence because he didn't want to be found, that should have been easy enough for him to do). So the question of if they ever find God depends on whether the actor would want to return.