Pod2G, one of the most active members of jailbreak community has announced current situation of iOS 5.1 untethered jailbreak. It seems that he and his team have all the exploits needed to develop new solutions to jailbreak. Now teams trying to bypass the ASLR ( Address Space Layout Randomization ), a tool consisting of placing certain key parts of the system at random position and was introduced with iOS 4.3 as extra security tool to prevent the jailbreak.
According to the pod2g twitter account iOS 5.1 jailbreak may take weeks before its completion. Specifically, pod2g says he has no idea when it will be released. "We have all the necessary exploits required for the jailbreak. I work to bypass ASLR on startup. "chpwn, another iPhone dev team member stresses, however, that even if we have all the pieces to jailbreak it may take weeks and month for a public release.