3 weeks are too early to give up, because they won't process clearing waitlist until close to the departure date - there is a plenty of time for them to sell BF seats.
In the past most of my upgrade happened about 3 days prior to departure. (last one was past August, so it was before waitlist priority change, I guess)
I have both experience: 1) upgrade cleared on one day before with almost BF-soldout flight, 2) didn't get upgrade with half empty BF seats when I checked 3 days before flight.

So you never know - don't give up the hope but don't be too optimistic.
BTW which flight on 12/16 ?