ever heard of russell wilson and doug flutie?
they're the exceptions, not the rule. I dont think he'll fail due to his height... I think he'll fail because to be a good NFL QB, you have to either insanely genetically gifted (even then, they often fail) and you have to WORK insanely hard in the film room.
Johnny football has some gifts, but he's no Vick genetically. I see him being too much of a party animal to spend his sat nights watching film like peyton or Brees or Russell wilson. I think he'll be partying.
We haven't seen him fall yet. once he does, once he gets wrecked for a few games, I think he'll appear entirely average.