The second half of August has had good availability of discounts recently. But, no one can know how things will pan out in August 2020, which is 18 months away. If resort bookings are soft, we'll see some good discounts. If resort bookings are high (and with the SWGE opening, we do expect them to be higher in 2020), they may limit the offers.
I tried to book a Free Dining bounceback discount at WL in 2017 for December 2018 and it wasn't available, although I was offered other options, including AKL (Note: I did book FD at WL for 2 adults in a nature room for July 2018). Also, Disney converted a lot of WL to Copper Creek villas, effectively reducing the resort size in half. For the recent set of general public room discounts, WL has been offered at 10% discount, while some resorts are receiving 30% discount. So, all of this indicates Disney has had less difficulty selling WL rooms at rack or with a small discount.
So, say you book your 3 rooms now. You may be lucky and Disney offers FD for your period *and* your check-in date qualifies *and* WL has availability under the discount/promo *and* you are able to modify your reservation to the FD promo. Great!
But, what often happens is that the promo may not be available for the resort or room type or check-in date. So, your group would need to decide if they are still going to WL on those dates and pay rack rate or close to it, or if they will change dates or resorts to fit in the promo. Booking the Room now simply guarantees you that room at rack rate. It does not give you any priority for a promo. The room has to be available with the promo for your exact dates in order to be able to have that reservation modified to Free Dining.
