We have sad news regarding the future fate of any Android 4.2 Updates for the Motorola Xoom and the Nexus S smartphone. Google's own Jean-Baptiste Queru recently made statements indicating that Android 4.2 will not be coming to either of these devices. Here's a quote from his post,
It's a shame that they aren't planning on moving forward with the update for those devices. They have the 4.1.2 version of Jelly Bean, but it appears something about the new features of 4.2 might be incompatible. Either that, or the company felt it was simply time to stop somewhere.-There is no support for 4.2 on Nexus S and Xoom. Those devices should
continue using 4.1.2.
Source: Google Groups via Phandroid