User blog comment:Master Sima Yi/Assassinews 05-08-'14 – Assassin's Creed: Rogue announced/@comment-4254431-20140905131951/@comment-3046679-20140905160511

No, he joined the Templars after a mission gone wrong, and when the Assassins heard of his switching sides, they tried to murder him, so he felt betrayed.

My point is, near the end of the game, when he's practically purged the colonial brotherhood, he'll have doubts and go "maybe this wasn't such a good idea, I can still make it right", and try to go after Haytham or somesuch, and get deadededed in the attempt. Because I doubt after successful wipe of the entire colonial branch, Haytham would just wave his best man away to another country or cut him loose entirely.