Actually, the myw sold by the ITR office on my base don't ever expire. I discovered it after we had to cancel the trip we had originally planned for October of 2020 and called at the time to check how long I had to use them, and was told they would never expire. However we are just now planning to take at the end of January. When I spoke to the woman at ITR she told me I would have to call and explain the situation and pay the difference between the cost when we purchased and the cost now, but when I called today and spoke to Disney I realised that it was only for the military salute tickets. I think it must be because the military salute tickets are significantly cheaper than the ones that are offered to other government personnel (like DOD, which is what my wife is) through the ITR office at the base. Those are so much cheaper than what you pay even on discounted sites but they certainly don't get as cheap as the salute tickets.
All that being said, I know for 100% fact that if you were to cancel for any reason, you would only pay the difference between the cost of the ticket you purchased now and whatever the cost of the ticket is when you end up going with the military salute tickets. And you can either do that over the phone prior to your trip, or at the gate. Honestly the difference on the military salute tickets don't change too dramatically year to year. (For example, if we'd had to pay the difference on our tickets, it was something like $15.) So at the most, if you had to wait a couple of years I can't see you having to pay more than $15 to $30 per ticket at the gate.
But if you're worried about it, I'd see what the turn around time on securing tickets is, and just wait a little longer to book. Park prices for military salute won't change between now and July.
