It appears that Google is making good on their promise to fix the December bug in Android 4.2 ‘soon’ with reports cropping up on XDA about an Android 4.2.1 update hitting both Nexus 4 and Nexus 10 devices right now. The only noticeable difference at this stage is that the update definitely fixes the bug which affected the events calendar in the People app, which you can see has now been resolved :
Over on XDA, one of the people who received the update has captured the path of the update for the Nexus 4 and you can download it here but unfortunately the update has not been captured for the Nexus 10.
No updates have hit the Galaxy Nexus or Nexus 7 from any of the threads I’ve seen on XDA as yet but I imagine that they will not be too far behind. Factory images on the Nexus Factory images page have yet to be updated but that too should change shortly to reflect the newest update.