So in the last episode it is revealed 'Prime' IS a rank and not a surname. Now it can be inferred that Jazz is second-in-command, because of the movie's influence, the fact that he's been close to that position in G1, and in the last episode, Jazz was the one who stopped Sentinel from overdoing the cleansing of the Autobots. If Sentinel was of a higher rank, he'd probably get Jazz to fish off like he tried on Optimus, but he didn't despite that being typical Sentinel, thus Jazz could be of a higher rank. That means the ranks goes as: Ultra (Magnus) Jazz?? Prime (Sentinel & Optimus) So that brings us to what will happen when Optimus becomes the leader. Maybe Prime (in the reverse role of TFTM86) reluctantly becomes leader and doesn't want to be called 'Ultra' out of modesty, over time the Autobots respect him as the 'Prime'.