I would bet that at least half of the 9 year olds on "the best" 9 year old travel teams never set foot on a high school baseball field. So forget about that. Keep him playing, make it fun. My opinion is the summer after 9th grade, then if college baseball is still his goal, get on a team that gets exposure, has a coach or organization that has contacts and goes to tournaments where they'll be seen. before that, just make sure he's learning and having fun.
I think this comes down again to defining 'best'. And as always when we have these conversations also differs from one area to another. Also there is the fact these kids are so young they have no idea what may be their favorite sports later on. But around here certainly they make high school teams if they choose to with few exceptions.