I did a lot of planning around historic dates when FD was offered in the past. I know there is no guarantee that it will be offered, but I am hoping that by using a reasonable thought process regarding timing that I have increased our chances of going when there will be a FD offer.
Having said that, yes, I already booked my trip, so we are going regardless of the offer. However, our plans will change a lot, if we have to pay for dining. We will be eating QS, with only 1 TS dinner for my daughter's birthday, as opposed to TS for every dinner. I will pack more snacks. We will probably have less free spending money for souvenirs. When push comes to shove, if I have to downgrade from a moderate to a value, I will do that as well.
Bottom line, if I have pay for meals, my spending in other areas will be less. The trip will still happen, but I will not be spending money as freely as I would if I had FD. Feeding 2 adults & 2 older teens is costly in WDW.