The answer: Sprint. According to a leaked document picked up by Engadget, Sprint employees will soon be trained and versed for the Nexus S 4G smartphone (fair enough) and the Motorola Xoom (what?). These training sessions are expected to start within a few days, and Engadget predicts that the products themselves will be released within a few weeks.
Sprint already has a product page up and running for the Nexus S 4G, still labeled with a "Coming Soon" note. But there's no mention of the Xoom tablet on the carrier's site...at least not yet.
Considering reviews have been mixed for the Xoom and sales haven't exactly met expectations, perhaps opening up the tablet to another carrier is just the boost that Motorola's Honeycomb-based tablet needs.