It's happening already. My son was 14U this year. We played in various level tournaments. Baseball Heaven, MSI, Perfect Game, Diamond Nation, Richmond County, Tag'em, BSE, etc. And, I lost count on how many times I saw a team playing where they had someone batting last and playing 2B or RF and the kid was a 12U or 11U player. It was obvious that it was a younger kid and he was way smaller than anyone else on the field. And, it was obvious that they were playing the younger kid because they couldn't enough 14U kids to play.
Then, on the flip side, you had teams playing with kids who were too old.
We played a US Elite team in MSI. Got crushed. Later we heard that they had two kids thrown out of the tournament because they were 16U playing in a 14U. The funny part was that the rest of the team was so good that they didn't need to have two 16Us to beat anyone.