The Motorola Xoom tablet has been around for a while now here in the states and you can pick one up if you want that runs on the sprint WiMax area. If you don’t like Sprint or live outside a WiMax area, that feature won't do you any good.
If your carrier of choice is AT&T, a version of the Xoom tablet has crossed the FCC test bench to get the approvals it needs the head to the AT&T network. The device is called the IHDT56ME1 and it has test reports talking about WCDMA bands II and V support meaning 850Mhz and 1900MHz.
Considering that those are the same bands that AT&T users for its mobile network the safe money says that the new tablet is bound for big blue. There is no indication when the tablet might land at this point.