You realize that this is equivalent to saying “Ignore what I said just before this”.
Yes, there has been no official notice of what December’s CD (or hopefully C-Weekend) will be. But it seems almost certain that there will be some sort of reprisal of all the CDs for the year, and highly likely that last year’s CDs will be folded into the event somehow. What we don’t know is the exact details of how it will shake out. Could be 2018 on Sat, 2019 on Sunday, could be all 2019 CD pokemon will occur more frequently in the wild, but both 2018 and 2019 CD moves are unlocked, etc. Or, they could do something completely different.
What we are all almost certain will happen is that players who started in 2019 (and by extension, everyone) will get a shot at getting the 2018 CD moves. Not sure how, not sure when, but it should happen.