The iPhone Dev Team is now currently working with i0n1c’s untether exploit, as mentioned on twitter:
Stefan (i0n1c) goes on to mention to not bother the iPhone Dev Team. If they are successful in their beta test, they can do whatever they want, and that includes possibly releasing a jailbreak tool for everyone. We can only hope, right?
i0n1c last demonstrated an untethered iOS 4.3.1 jailbreak running on his iPod touch 4G.