While Chronic and iPhone Dev Team, two highly recognized figures in all that is Apple jailbreak related are working on an iOS 4.1 jailbreak which would be based on the SHAtter exploit but it looks like the need of SHAtter might not be necessary after all. Instead there is a baseband exploit which will let you jailbreak your iOS 4.1 iPhone 3GS.
The 05.14.02 exploit was discovered by a hacker named Clayton and the work has yet to be given a thumbs up by a member of the iPhone Dev team, The exploit causes your iPhone 3GS to crash when it is issued a certain command to the baseband, This shows potential for an unlock being made available very soon. The jailbreak may not only be compatible with the iPhone 3GS but can also be used to unlock the iPhone 4. Clayton stated that this exploit may or may not be vulnerable but it's definitely more vulnerable than the other 3 exploits he tried out to achieve this.
Although the unlock does have potential an official release is still far for now this is still in testing phases.
Here is a video showing the Baseband Exploit in action:
Source: Redmond Pie