The iPhone-Dev team dashed avid jailbreakers’ hopes with a morning post (via Ars) explaining that with iOS 5 Apple upped the ante in its cat-and-mouse game with the jailbreak community. According to the team, starting at iOS 5 and onward you will no longer be able to use iTunes to restore to previous firmware versions using saved SHSH blobs (created with tools such as Cydia or TinyUmbrella). Previously, jailbreakers always had peace of mind knowing they could revert back to a previous firmware should anything go wrong.
“Apple will be able to flip that switch off and on at will”, the team warns, adding that “tethered jailbreaks will still always be possible for devices where limera1n applies”. You will also be able to restore to pre-iOS 5.0 versions (with saved blobs) provided you carry out the procedure using an older iTunes version. This wasn’t entirely unexpected, the team wrote:
Apple, of course, is attempting to give the community fewer reasons to jailbreak by overhauling the notifications system with the all-new Notification Center, invoked with a pull-down gesture. The list of features Apple borrowed from unofficial tweaks and modifications also includes handy widgets. In addition, an Apple patent application indicates they might at some point decide to allow third-party widgets in the iOS 5 Notification Center, even if they are already technically feasible.
