There was a poster here awhile back, and if I recall correctly, their DS accepted USNA over NROTC, however, within days he decided it was not a fit. He contacted NROTC and the school, and managed to get the scholarship back, but they waited weeks for the answer, they had to get approval to re-activate it.
The issue for you is that was a few yrs back, and now with the budget and the economy I am not sure these options will be as easy as they were yrs ago. It has not only become highly competitive for the SA's, but also the ROTC scholarship program.
The reason many take plan B, by paying a deposit, which the NROTC poster did was the in case problem at BCT. That is also why many say to pay it, because if you look at it from a different perspective it is still a win-win.
You pay 300 bucks to hold the spot, if they stay after BCT you lost 300, but still you are not paying tuition. If they are one of the 5% that do not graduate from BCT than they have a spot at Plan B College. Yes, you may not get the scholarship, but the question that you need to answer is what than?
I can say it is rare that they get medically turned back or leave BCT, but it does happen. These parents will post on this forum for direction. Reason why? Because they didn't pay a deposit and now their child's only option is Community college. Nothing wrong with a CC, but if they are a medical turnback, than they have to deal with their child's emotions and medical issues, plus running around in August to get them into classes they need at the level of the SA. If they left voluntarily, it is still an emotional issue, and now they went from an Ivy league standard to a CC while their buds are packing up to go to their plan A. Remember these kids are 18, emotions are every where on the scale, and vary second by second.
21 yrs as an AD wife, and I will say we always planned and plotted for the "what if". It was seen as insurance to us. I guess that is where I started living by the cliche "hope for the best, be prepared for the worst".
I am not trying to be raincloud. I am just saying, always keep plan B alive until you need to make a new plan B. Accept the appointment, just pay the deposit. Ask yourself, what if? Will your DS be able to adjust back if he has to go to CC? Will you be able to pay without a scholarship. Contrary to belief, you can apply for FAFSA in Aug for an incoming student, plus, most if not all universities now offer 0% int monthly payments. For our kid because they made Dean's list 1st sem. freshman they opened up more scholarships only eligible to them. There are multitude of ways of paying if you have to go Plan B short notice. I also know many parents who have a strong credit score that they take those 0% interest credit cards to pay for fall, and than they apply for a private loan for their children with the bank, I think they stated it takes about 3 weeks to implement. (Not sure, just what the kids have said) Talk to his plan B school now, and the CoC, see if they can also place a plan B in place for the what if. They maybe able to assist you more than you can imagine.
Good luck