Android version of the test is unknown, Jelly Bean expected
Update: Shortly after the soak testers started getting emails, Verizon made 4.2 official for everyone with a Xoom. We're not sure if they still have something special planned for testers or if they're done with the Xoom.
Update 2: It seems that the soak test has begun, and it is for Android 4.1.2 — despite the official Verizon page (see screen shot after the break). We may see a retraction from Verizon soon.
Almost 3 months after the initial invites were sent out by Motorola, emails telling participants that the soak test for the Verizon Motorola Xoom 4G LTE will soon begin and finally being sent. At the time when the invitations initially went out, it was expected that Xoom owners would get a version of Android 4.1 Jelly Bean to test, or maybe Android 4.2. Now that more time has passed, and Android 4.3 has been released, things could change — although it is unlikely.
It would make sense for Motorola to bring the Verizon Xoom up to the same Android version as its WiFi-only sibling, Android 4.1.2. We won't know for sure until builds become available to those participating in the soak test, which should be any time now. Verizon Xoom owners that received an invite back in May, make sure to keep an eye on your inbox.