I think if Trask is still here, he starts. If Trask leaves, Franks might stay unless someone convinces him he has a decent shot at the NFL at this point. If Franks is still here, with no Trask in front of him, then Franks would probably start, but with a fairly short leash to put EJ in if Franks is underperforming. Once EJ gets a few full drives under his belt, he would likely beat out Franks for the remainder of the year. Obviously, if Franks and Trask are gone, EJ is the starter.
This is not what I want to happen, but based on Mullen's loyalty to his more senior players, it's what I think WOULD happen.