Agreed. The footwork, speed and offensive flow of soccer really helps with all sports, IMO. It certainly has helped my 12YO get the offensive flow of ice hockey.
Yep, dude is 5'1" going into the 4th grade. I fully expect him to be at eye level with me going into middle school.
How tall are you?
I was always the tallest growing up... very rarely meeting someone my age that was taller. I always thought I was 6'1'' as I was in 8th grade and stopped. Literally always thought this... I think I did grow more and maybe 6'2" or 6'2 1/2. I just found this out this morning. No joke.
So, Thursday I took my older son to the Notre Dame Jr High Football camp. Standing waiting for my son to get some autographs from the coaching staff, one camper was next to me and taller than me. He couldn't be more than 8th grade and would have been roughly an inch or two taller than me. I said something to him about being in 8th and he said he was 6'4 1/2" and I balked at it saying I was 6'1" and he had and inch or two on me. He replied that he had just been at the Dr's appointment and that was the measurement (which I figure with him being that tall that they would take extra care to get a good measurement on him). So, this morning, I tried to measure myself and I am taller than 6'1" for sure.

Hard to get a real good measurement doing it yourself but no doubt taller than 6'1".
Anyways, yes, I would get him exposed to a bunch of sports and have do multiple sports at least up to Jr High. I really am a proponent for multi sports even if one sport has been signaled out as their love. Others sports help develop and train them as well in ways that doing one can not (soccer being an example, you can not improve footwork as well focusing on basketball as you can taking some time to play soccer). It also helps keep them fresh and away from burnout. I mean, the number of kids who drop sports in HS is tremendous and not an insignificant number were one sport athletes who just tire of their sport. It also helps avoid injury from overuse and wearing down concentrated muscle groups.
I would consider these sports as the best compliments to development in basketball:
- Swim, unmatched for development of strength, conditioning, lung capacity, explosiveness, etc- all with almost no injury risk and no stressing of his joints etc. (at that size, that is a huge plus, at these ages maybe does not notice it but building him up with saving wear and tear on his body is huge). There is different thoughts on competitive swimming assisting in height growth as well so there may or may not be helpful to get the most out of his height- my view is it will certainly not hurt and the decompression of the spine while swimming certainly can't hold him back. Huge advocate for swimming for most athletes but would strongly push you to explore it for him.
- Soccer (as much as I am not a fan of the sport itself), as discussed footwork is unmatched. Develops agility and endurance. Using your body and positioning to protect the ball. Spacing and off ball movement as well.
- Volleyball, the obvious point here is jumping. Plus, it may end up being a good sport for him anyways with his height. Also, agility, explosiveness, hand speed and reflex development.