NutCase

Remember how Ruin couldn't get the atium due to kelsier destroying the pits and elend's army burning the entire supply? When kelsier tells the crew about how he destroyed the pits, he says he stopped the production of atium for approximately 300 years. That means that very soon after the events of Bands of Mourning, in Mistborn era 2, the atium will start to 'grow' again in the pits. If sazed were to take this atium and absorb it as power, it would be pure Ruin power. This would lead to sazed's ruin side being stronger than his preservation side, because preservation used some of his power to create intelligent life. I think maybe then sazed will become discord: when his ruin outweighs his preservation.