I'm a parent and manager of a 13yr old travel team. I agree that when the kids move up to the big field, the herd thins out quite a bit. Kids aren't "pushed" as much from mom and dad to play ball. There are other options for kids. I think the borderline kids are weeded out at 13, and by 14, you'll mostly see the kids that are dedicated. Since there are no must-play rules at this age, kids that aren't that good don't want to sit the bench (I don't blame them).
I totally agree about the kids who were stars in LL but now are just average. I see it all the time. Problem is, they still think they're stars... These kids still think that they don't need to work hard to improve. Reality will kick in soon for them...
I just sent an email out to me team and said that next year's team will revolve around pitching and defense, so the kids who can only hit (and granted, they can hit) will possibly be left behind. To me, playing good "D" entails hard work and effort, not just talent. I don't need 5 firstbasemen!!!