A FlyerTalk Posting Legend
Join Date: Sep 2012
Location: SFO
Programs: AC SE MM, BA Gold, SQ Silver, Bonvoy Tit LTG, Hyatt Glob, HH Diamond
Posts: 44,454
Given that it shows as a benefit you've earned, I'm cautiously optimistic that on Jan 1 it will just kick in.
On the other hand, they might not want to level up your status until late December flights have had a chance to post.