iPhone Dev team has just published a post titled “Blob-o-riffic”, which provides details about downgrading from iOS 6 to iOS 5.x.x.
iPhone Dev team has warned that iPhone 4S, iPad 3 (and some iPad 2) users won’t be able to downgrade from iOS 6 to iOS 5.1.1 once Apple stops signing iOS 5.1.1 and will be stuck until a jailbreak for iOS 6 is released.