Just last week Google released the JZO54K build of Jelly Bean for the Nexus 7. This is Android version 4.1.2, and although it hasn't been officially released for the Motorola Xoom, there is a method to get it on the WiFi edition of the device. Some folks over at XDA figured out how to make the ROM work on the WiFi Xoom before any official rollout. Here's a quote with the details:

In case you’re wondering how they were able to get the file ahead of the official roll out, you have to thank soak testers who received an OTA update of the JZO54K build of Jelly Bean. It was only a matter of time before they were able to track the URL down on Google’s server, which allows others to manually download the 7.3MB file and install it on their device.

Installing the file shouldn’t be hard, as you can easily use the update via USB option in stock recovery, the details of which you can find on the following thread at XDA. You can also use the ADB sideload method as well, which means you don’t even need to use a USB stick to apply the update.
Source: AndroidAuthority