I would normally completely agree with you, but this is an extenuating circumstance that goes well beyond someone simply changing their mind or altering a schedule that's completely within their own control. If the OP is already wisely making other arrangements and they come through, yeah, sure, cancel as early as possible for the potential benefit of others. If it clears up though, great, he's still covered, hedges his bets, and saves his original trip. If it doesn't, I have my doubts that the daily quota of 25 people is going to be met by demand in these conditions anyhow.I am going to disagree with that last advice. If you know you are not going to use your permit, please cancel it so that the rangers can put it into play immediately, rather than waiting for you to show up, and then offering it to someone much later in the day when you fail to appear...
He's waiting to see what smoke and fire are going to do, not to see if Aunt Mildred is actually going to go through with her 4th wedding, or if something better comes along between now and August 1st. That would be rude and upsetting, but even if I was standing in line at TM waiting for the exact same permit that day, I think I would give him a freebie and be okay with waiting another couple hours on this one.
