“All Motorola XOOM tablets on the Verizon Wireless network are eligible to receive an upgrade to support 4G LTE. This includes those that have been unlocked; however, those units must be submitted for upgrade with the original factory software reinstalled and the device relocked in order to receive the upgrade.
For devices that are returned unlocked, Motorola will attempt to complete the upgrade, but may be unable to update the software. In these cases, the device will be returned to the consumer with just the 4G LTE modem installed.”
What doesn’t really make much sense is that Motorola actually allowed for the XOOM to be unlocked so developers could do more with the device. So not supporting and upgrade on unlocked devices seems to go against its original intent.