I think either way the path forward is clear.
A: Alabama has to have Milroe as ready to go as possible, even if Young plays there's no guarantee he can keep playing or doesn't reinjure. That is kind of stating the obvious but I hope Alabama doesn't start gameplanning for Young as the starter anytime soon, I think it should be all about Milroe for the time being.
B: Alabama has to develop the running game more. Even if Young is playing, heck even if he's healthy... the safest play for the QB is handing off. GMac won a championship game with broken ribs by relying on the running game, and while I get that times have changed, the running game protects the QB. The more Alabama can run effectively, the less of a concern Young's injury becomes.