MuscleNerd announced that they ‘will coordinate ultrasn0w iOS5 compatibility update to come out *after* a planned MobileSubstrate update tomorrow’. Please understand that they won’t release a brand new ultrasn0w. They will just update the existing one with iOS5 support and old baseband.
Also, please understand that ‘after a planned MobileSubstrate update tomorrow’, doesn’t ( necessarily ) mean it will be released 3 seconds after the MobileSubstrate update is released. Once MobileSubstrate is updated, they will have to start checking compatibility and then release the updated (patched) ultrasn0w.