Sharing here in case it's helpful - Our DS negotiated everything up front and was transparent with ROTC and the Plan B University Admissions Dept. He knew he had an appointment, but enrolled anyway to save his space at the school and in ROTC in case something happen...an injury, change of plans, whatever. Or it could be in the event that an applicant is still waiting to find out if they will receive an appointment.
The Plan B University was more than happy to work with a student that is trying to serve and we found they really appreciated the student's desire to plan ahead. To build goodwill he was very straight forward with the university and told them, if not for the appointment, your school is my other choice and would be honored if I could attend if that's the way things play out.
He received refunds form both housing and admissions when they were informed he had made it through basic and would be continuing at USAFA. Took a few phone calls and he kept good records, but it all worked out.
Hope this helps for those that might find themselves waiting, or need their Plan B just in case.