Please post a CHRISTMAS bonus skill.
AFAIR, last year they were published(°) then... removed a few days later. And I don't remember they came back later.
So it's unsure they'll be back this year (at least, I wouldn't bet on that).
(°) for courses that have one, of course. Namely the courses originally created by staff.
The 10 first courses, which have been created by Duo staff: German, Spanish, French, Italian and Portuguese for English speakers, and English for German speakers(°), for Spanish speakers, for French speakers, for Italian speakers and for Portuguese speakers. See for example here.
(°) Not even sure that one has them.
Duolingo will post the Christmas bonus skill (for those languages that have a Christmas bonus skill) when it's ready.
Better to wait until it is ready, in fact. Last year, their was some glitch or problem and Duolingo had to pull the skill very shortly after releasing it. I don't think that issue was related to releasing the skill too early, but issues of that type are more apt to happen when not enough time is allowed for a project.