The Dev-Team could be working on an unlock for iPhone users who have already updated to official firmware 3.1.3 and find themselves stuck with no unlock options at the moment. Sherif Hashim has discovered an exploit that could be used to unlock the current iPhone baseband so the iPhone can be used with carriers other than AT&T.
This exploit was verified by Dev-Team's own MuscleNerd as a legitimate and working exploit. It's possible the Dev-Team would wait until the release of iPhone OS 4.0 on the next generation iPhone before revealing the exploit to Apple with a new unlock, however the new iPhone isn't expected to ship until later this summer.
MuscleNerd will defer to the Dev-Team's opinion on when to release the 5.12 unlock. Sherif Hashim's exploit uses a previously undiscovered security flaw that makes it possible to unlock the baseband.
Many iPhone users are already running the latest baseband (05.12.01) and can't downgrade to unlock their devices. The baseband refers to software that runs the iPhone's cellular modem, the hardware that communicates with the wireless network.