It has been said that the greatest curse you can place upon someone is to label them as having "unlimited potential". The expectation that players will improve month over month and year over year isn't realistic especially when it comes to teenagers. The sad reality is that sometimes you peak at eighteen. The talent/skill maxes-out, the hockey sense maxes-out and the love of the game wanes when you've always been the best player on your team and now find yourself struggling on the third line at this level. Given how much families have sacrificed to get their child to this level it must be a difficult conversation to have as the dream/desire comes to an end and their education package is the only pay day. Most of these kids will never play professionally, they are simply the players that help the few that do play professionally develop.
Not too sure what this post is trying to tell us, any player making it to the best junior hockey league league in the world (CHL/OHL) had to have some great talent to be at this level. No age is set to further on to pro-leagues, if look only two former Knights Steve Smith and Brandon Prust whom were never drafted at the junior level went on to successful NHL careers, makes this post above void. What hapens from here is all up to the players, you can be sure no one will quit because they are 18 and think they don't have a shot at pro-hockey.
Look at Jacob Julien , late to thew party at under 18 drafted into junior and now a NHL draftee. Everyone has a crack at pros in this league until they leave at 21. I remember Steve Rucchin playing Junior D with Thamesford then on to Western University he was there 2 or three years when Anaheim signed him right out of London University hockey and he had long NHL career. There are no age set or lack of talent preventing players at the OHL level, to reach pros, it's all out of will powers, it all depends on the player's mental and physical endurance how far he will go. IMHO