Still waiting for that official Android 4.0 firmware upgrade?, well for Motorola has already started the delivery of the latest Xoom Android 4.0 ICS firmware for select Wi-Fi users, if you haven’t received the firmware upgrade yet then you will hopefully be getting it soon. Currently it is available to the limited no. of users so that Motorola can test for major bugs and remove them before a major release.
If you can’t wait you can also check out this Android 4.0 ICS firmware at XDA Forums:
Download Xoom Android 4.0 ICS Firmware AOSP : ROM Download (Latest version 12th January 2012)| Thread Link (Android Open Source Project)
As Google has already added the code to AOSP the above ROM is best you can get for now.