Just two weeks ago, Comex, the developer behind JailbreakMe and Spirit jailbreak tools has confirmed the arrival of userland untethered jailbreak for iOS 4.2.1 to be released soon.
Today, MuscleNerd of the iPhone Dev Team has confirmed the same. In a deleted tweet spotted by RedmondPie claims that a untethered jailbreak solution for iOS 4.2.1 is indeed in works, and that it will be ready for prime-time use somewhere around 2011.