Steam Award Cards

I should probably let people who know more answer but I believe they do disappear if you don't trade or sell them before they expire.
The date is usually a few weeks after the sale event ends.

https://store.steampowered.com/steamawards
Scroll down to the FAQ, right side is the "Trading Card FAQ"
It links to their blog post on the subject:
https://steamcommunity.com/groups/tradingcards/announcements/detail/1818796702570011884
It use to be that they disappear at the end of the sale but as of that blog post, 2019, they changed it, just read the wording though, will only stay if you have enough to craft a badge ...

If you see the card description on the inventory screen it shows the crafting and trading deadline. But enough cards for the badge overrides it and keeps them hidden so you cant trade.

off topic but are these cards already dropping or you have to wait for december 22?