You can unlock your jailbroken iPhone right now thanks to an iPhone hacker called Loktar_Sun. The iPhone unlock relies on a project made by iOS developer Sam Bingner dubbed SAM, which stands for Subscriber Artificial Module. Loktar_Sun used SAM in an unexpected way, reusing the IMSI obtained in an early step by adding it to a later step. Renowned iPhone hacker MuscleNerd has confirmed via his Twitter that this unlock method works with his iPhone 4S:
Instructions for performing your unlock can be found from this link as MuscleNerd Tweeted earlier. According to Sam Bingner, this unlock method grabs a legitimate ticket from Apple and does some information spoofing to unlock your iPhone. Sam was able to confirm that it also works with the iPhone 4. While the instructions are currently a little long, Sam says he is working on a package to make it much more simple and straightforward as we speak.
To download the correct SAM package, be sure to add the following repository to your iPhone in Cydia by tapping on the Manage tab, then the Sources button, then tapping Edit, then tapping Add:
MuscleNerd also states that if Apple fixes this unlock method, your unlock should still be valid.