According to the tweet Muscle Nerd confirmed that Geohot is already working untethered iOS4.2.1jailbreak solution , But will not work for i devices.When iPodguy79 tweeted:
@sherif_hashim @MuscleNerd @iphone_dev @chpwn keep up with your soap opera and geo will be slapping another reality check on you
Musclenerd Replied: @ipodguy79 I hear geohot does have an untether actually! Though not for all devices.
On the other hand, Dev Team is still ironing out bugs that are lurking the final release of redsn0w 0.9.7 which support untethered jailbreak. Comex’s upcoming untethered jailbreak for iOS 4.2.1 is probably going to be a Cydia package over your existing Redsn0w tethered jailbreak but no ETA has been cited so far!
While we’re not sure about the status of that window, we do know that the untethered jailbreak software will be released very soon. Stay with us as we will get more information we will update you.