Honestly a New Years party would be kinda lame. Not the party itself, but the timing in the episode. Since the Christmas party just happened, and we aren't even at actual Christmas yet, that means either the majority of Episode 12 will be in-between Christmas and New Years so that the New Years party is set towards the end of the episode (like with 10 and 11), or the party is set towards the beginning/middle of the episode, which is weird pacing-wise.
Or third option, something happens where we can't have a New Years party, so we throw one for something else.