There is progress in the untethered jailbreak on the iPhone 4S, according to the lastest blog from Pod2g.
Earlier the anonymous developer had reported that the iOS 5 untethered jailbreak was working on other devices, including the iPad 1, iPhone 4 and iPod fourth generation. Though Pod2g has developed an untethered jailbreak for devices functioning with A4 processors, he has so far not been able to find a solution for devices working with A5 processors.
In the case of the iPhone 4S, he had initial difficulties in making advances. The specific reason that he gave were related to processor cache issues.
The updated blog states that there are no more cache troubles. He has stated, OK, figured it out, the A5 cache is not a problem anymore. I sorted it out by doing the untether in a single thread and by flushing all the dcache then all the icache in a row at a strategical point of the process. He has provided a link explaining issues related to the self-modifying code on the ARM platform.
After the processor cache issues are fixed he says he will be extremely close to a properly implementable untethered jailbreak on iPhone 4S. Pod2G has also informed that he would keep everyone updated of the progress achieved.