iOS 4.1 Jailbreak not available yet, Jailbroken iPhones should avoid iOS 4.1 for now
Today you’ll likely start seeing iTunes innocently offer you a new version of iOS…version 4.1. Don’t accept it…it’s a trap!
The “It’s a trap!” message might be a bit dramatic, but basically they are saying that if you download the update you may lose the ability to jailbreak your iOS device again due to the iPhone baseband update that is included:
…There’s currently no known way to revert your baseband — if you update your baseband you’ll lose the ultrasn0w unlock, possible forever.
Please stay away from this 4.1 release until a safe jailbreak procedure (which also preserves ultrasn0w) is developed and released.
If you have a jailbroken iPhone, avoid iOS 4.1 for now. This isn’t a really big deal considering how fast the iPhone Dev Team works, the chances of them having a new jailbreak available shortly is pretty high.
Update: The Dev Team has announced that 4.1 is susceptible to jailbreak after all thanks to a boot ROM exploit. More to come.