After some research, it all falls down to just one announcement by Sprint.
It looks like, to me, that someone got a little dyslexic with their numbers, announcing Android 4.2.1 OTA push rather than 4.1.2, which is the latest I have on my tablet.
This I based on the fact that the firmware they mention in the announcement matches the firmware listed in my device, it's just the last two numbers reversed.
My problem is just that I was hoping to be able to take advantage of the multiple profiles feature that came out with 4.2.x.
Frankly, I doubt Sprint will push the firmware any further... they are pretty lackadaisical about updating any equipment more than a year old or so.