I think all hands will get a shot at earning the starting spot, including TA.
I think Riley will make it work with what he has next year. As far as the long term is concerned, its not that inconceivable that we start seeing recruits at the QB position that are less of the "multiple"/raw talent athlete type that can run a variant of the option and then pass and more of a 6'4"/6'5" type of pocket QB that is a good athlete (e.g., can move laterally to buy time in the pocket) and a far more polished passer and reader of defenses.