Since it only Got last 4.0.4 update by Motorola and everone wants to be on new Android 5.0 Lollipop version , so Schischu made a Android 5.1.1 Lollipop based Custom Rom for Motorola Xoom .
The Custom Rom is currently in Alpha stage ! It cannot be used for daily use , still you can install it following the below steps .
How to Update Motorola Xoom to Android 5.1.1 Lollipop by OmniRom -
Step 1. Download the Rom from below .
Step 2. Boot to custom recovery mode and wipe dalvik cache , cache , system and data .
Step 3. Install Omni Rom 5.1.1 Lollipop Rom , you downloaded following Step 1.
Step 4. Install Gapps and Superuser for installing Google Apps and rooting your device after that .
Step 5. Reboot your Motorola Xoom .
OmniRom Lollipop - Download Here