Dev team has already released Redsn0w for iOS 5 for Mac, which includes the PwnageTool functionality and iH8sn0w had released Snowbreeze for Windows that allows users to preserve iPhone’s baseband while upgrading to iOS 5.
MuscleNerd tweeted few minutes back:
will coordinate ultrasn0w iOS5 compatibility update to come out *after* a planned MobileSubstrate update tomorrow
Please note that we’re assuming that Dev team will release it as soon as MobileSubstrate is released, but it is possible that it is released a little later.
Ultrasn0w currently supports the following basebands 01.59.00 (iPhone 4), baseband 04.26.08, 05.11.07, 05.12.01, 05.13.04 and 06.15.00 (iPhone 3GS). We don’t expect it to support latest basebands such as 04.11.08 (iPhone 4) or baseband 05.16.05 (iPhone 3GS) that comes bundled with iOS 5 that was released yesterday. Note: You can find your iPhone’s baseband by going to Settings –> About –> Modem Firmware
So Ultrasn0w for iOS 5 will be useful only for users who have iPhones with the older basebands mentioned above, unless Dev team has a surprise for us.