I think it's likely that more closed resorts will reopen, if the downward Covid trajectory continues. If that happens, there will be more availability at those newly-opened resorts. AKL Jambo will reopen soon, so it had a lot of availability, for example.
I just read on a Disney blog that it’s a staffing shortage and has nothing to do with covid. More hotels and eateries will open as soon as WDW can get enough employees to work at the hotels, restaurants etc.
I tried using David’s and other brokers a few times but they never had inventory of points for the higher demand resorts we liked.
So we started renting personally from owners on the boards which has worked out great.
Unfortunately DVC is near fully booked already early December. Only the odd day or two, probably just find something like AKV &/or OKW Dec 6&7 standard studio.
This is what we did for our December stay this year. I booked it a month or so ago, and we still had to split our stay to get all nights - no one category was available (AKL) for the full stay.