For every guy who doesn't make it, there comes a point when you make a determination that he isn't likely to develop into what you want. Often times it's when you're scouting him. Maybe it's when you get him in camp, preseason, or after a certain amount of game time.
You obviously think that the skill set and progress you see in EJ warrants further evaluation. I actually agree, but I'm sure my leash would be considerably shorter than yours.
The point is, you're really not arguing over the wisdom of developing a young QB, you're arguing the likelihood of EJ becoming that guy relative to the opportunity cost of sticking with him beyond a certain point.