There are also some rumors on Twitter of the update package being available directly from the Google servers. The official update from Motorola will require your Xoom to be un-rooted. I'm not certain at this point if this download directly from Google will work with un-rooted devices or not.
The direct download appears to be update file HMJ37, which is the same version that is seen on Xoom's that have gotten the update through normal update notification. Download and go-it-alone, or just be patient. The update is coming for you soon, one way or the other.