The AOSP has been tagged as 4.2.1 r1.2, and the small change log lists a few interesting bug fixes. Version JOP40G will have some power management fixes as well as a tweak to the way an EXT4 partition handles file creation. These fixes are not device specific, so they will affect the Nexus 10, Nexus 7, and Nexus 4. We imagine the Galaxy Nexus will also see the benefits of this build.
In a nutshell -- some folks had issues where their device would shut off when removed from the charger, and these changes should address those. No word on when to expect an update, or if one is planned for this tag. There's plenty of bugs to squash in 4.2.1, and like we have seen with every other build of AOSP these things take a little time -- often longer than we would like. Maybe OEMs holding off and not delivering the bleeding edge for their phones isn't such a bad idea, right?