we're all wondering the same thing, heh.
last year was the first year that TBT hosted a Christmas event-- you can find the official threads about it archived on the Bulletin Board section. last year there were also glowing holiday lights that you could purchase in the shop on december 1 as a temporary collectible. i don't believe any winter or Christmas items were available in previous years, mainly because the forum had instead hosted the TBT Fair event in december for several years prior.
I havent seen a Belltree Direct or any mention from staff as to whether or not there will be events or collectibles this month. but this year's halloween event dropped without prior notice, so perhaps that's how things will typically operate now going forward....