I think you (should) need either to be a large part of two championships or one plus 10 or more years on the team in order to get your number retired. Al has an outside shot at the first one, but I don't think being the 3rd-to-5th best player would be enough (I also don't think KG and Ray belong up there, as much as I love KG)
It would make him a sure-fire hall of famer when you consider his college and pro career, but I don't think it would be enough for getting his number retired