I'll provide my view and my son's experience. First, my view. I believe kids should play the sports they want and enjoy the experience. A kid only gets to be a high school stud once. Enjoy the experience. That said, I told my son he might have to make some decisions down the road if playing college baseball becomes viable. He was playing three sports. I told him he might have to cut back to two to have an off season for training.
Before middle school my son played soccer, basketball and baseball at the rec and travel level. In middle school we let him play football. He continued to play travel soccer and the other sports. The offensive coordinator was geeked up about training my son to become the QB junior year.
Entering high school it took a week to decide banging in football and fall baseball were not a good mix. He walked away from football. He begged the soccer coach to take him despite missing summer sessions. He played JV freshman year. The soccer coach had him as the goalie going back to when he was ten. He was the point guard on freshman basketball. He was the shortstop and a pitcher on JV baseball. In the winter he attended three 5am baseball practices per week. He skip them on game days.
in he summer he played travel baseball, went to goalie camp and worked on his basketball on his own. I told him he may have to drop a sport by junior year to give more focus to baseball.
Soph year he was the starting varsity goalie. He was the projected varsity shortstop. I expected him to be the JV point guard. Some expected him to make varsity due to his passing and defense.
The basketball coach had other ideas. He wasn't happy my son didn't attend off season workouts in the fall. He was playing soccer and fall ball. He didn't play summer basketball. He was playing travel and did two weeks of goalie camp. My son was cut from basketball. Everyone was shocked.
My son was going to talk with the basketball coach the next day. I ran into him at the grocery store that night. We're friends. We had a good discussion about the situation.
He said if my son was only playing basketball and one other sport it would have been ok. But skipping all the offseason work was not ok (even though talent wise he belonged in the program).
My son was bummed. Soccer is his best sport. But he loves basketball as much as baseball. I believe he could have played college ball in any of the sports. He rationalized the situation as the basketball coach made the decision for him about playing a third sport and having an off season to train for baseball.
His baseball game took a giant leap that year. Part of it was getting bigger and stronger. Part of that was not running off weight playing basketball. Plus he lifted like crazy. He focused and worked hard on his swing and pitching mechanics that winter. It made a huge difference in who he was as a baseball player.
Looking back he knows having winters off before baseball turned out to be the best thing for him. He played three years of varsity soccer and baseball.