The Motorola XOOM is already available both in a WiFi-only flavor as well as a version compatible with Verizon's network, with a Sprint-ready model on the way. It doesn't appear that the XOOM's tour of carriers will end there, though, as Moto's slate may be coming to both AT&T and U.S. Cellular in the near future, too. First up, we've got an FCC filing that shows a Motorola-made "wireless tablet" known affectionately as the IHDT56ME1 getting approved for use on the 850 and 1900MHz bands, which just so happen to be the very same ones that products in ATT's lineup use for 3G. Although this isn't exactly irrefutable proof that the XOOM is coming to AT&T, the fact that there aren't any other Moto tablets in existence (that we know of) suggests that Ma Bell is indeed getting the 10.1-inch Honeycomb slate.
Next up we've got evidence that the XOOM could soon be calling another CDMA carrier home. The folks at Android Central recently posted a screenshot claiming that U.S. Cellular will soon be adding the XOOM to its stable of devices. Unfortunately, there's no mention of whether USCC will be offering the WiFi-only model or something that can actually access their cellular network, but the image does show that the target launch window for the device is sometime in the second quarter.
The XOOM is a pretty big deal for both Motorola and Android, so it's not terribly surprising to see the slate make its way to even more carriers. It's not clear exactly when we'll be hearing more about the XOOM from either AT&T or U.S. Cellular, but you can bet that we'll keep you updated as more details come to light.