It would be easiest to get it renewed now while you have free time. You can renew it at USMA, but finding time to do it can be a problem. If you travel on USMA business (such as spending a semester abroad or traveling on an AIAD) you will be issued an official government passport, but that is for use ONLY on official business, not personal travel.
A passport is not required. It is a good idea to get one before R-day so he has it for future trips. For example, my son is going to France over spring break as part of a history dept trip. The cadets that are going are supposed to use their regular passports and not the official government ones.