Depends where he's coming from. If it was 12u Little League at 46', then jumping to 60' can be a bit much. It's not that it's not doable. But I prefer a more gradual progression so kids don't do things like altering throwing mechanics just to make the distance. But, either way, I wouldn't get too worried about it.
If making the jump to 60', start practicing it early and gradually even if that means practicing on your own before the team starts practicing/playing at that distance. This will help avoid a sore arm later.