Although iOS hacker iH8sn0w said yesterday that he is not going to upgrade the p0sixspwn package for untethered of iOS 6.1.6, the package has just been updated on Cydia.
Unfortunately, the information για το βοηθητικό πρόγραμμα του p0sixspwn it is yet to be released so you will need to jailbreak via RedSn0w in order to apply untether after Cydia is installed on tether.
Of course, it's easier to upgrade to iOS 7.0.6 and jailbreak to use evasi0n7.
But if you are one of the fanatical fans of iOS 6.XX you can find the p0sixpwn package in the "System" section of Cydia. Note that its description is wrong “for iOS 6.1.3-6.1.5”. THE version 1.4 supports iOS 6.1.6.