On Twitter, Sheriff Hashim, a prominent member of the Dev Team that focuses on baseband and unlock, has confirmed that the release of all iPhone iOS 4 upgraded to 4.1 or 4.2.1 will be made public by the middle of January 2011.

This means that work on the construction of a new tool (probably a updating Ultrasn0w) are now well advanced, That provided by the Sheriff Hashim, though limited, is by far the first ETA (estimated date of issue) dell'unlock baseband for the last 4 iPhone firmware released by Apple.