Crossing my fingers on that JB being available for the ipad4. Just got one recently!
Heres a full list of devices that will be supported by 6.1 untether:
iPhone 5
iPhone 4S
iPhone 4
iPhone 3GS
iPad 4
iPad 3
iPad 2
iPad mini
iPod touch 4
iPod touch 5
Apple TV 2
http://www.redmondpie.com/ios-6-jailbreak-untethered-device-compatibility-and-expected-release-date/