Apple released iOS 4.3 beta to developers this week, and it certainly didn’t take long for folks to figure out that you can tweak the existing jailbreak tools to open up an iDevice running the latest operating system to run officially unsupported code. Redmond Pie has the step by step directions for using a modified version of the PwnageTool with the Limera1n exploit.
As for carrier unlocking a phone so that it can be used on different networks, that’s likely in the works… but iOS Dev Team member MuscleNerd says the unlock tool won’t be released until after iOS 4.2.5 or iOS 4.3 is publicly available. Right now only a limited number of beta testers have access… and there’s a better chance of releasing software based on exploits and having it stick around a while if you release it after Apple’s software is out of the beta testing period. Apple doesn’t like to push updates to its “final” software too frequently.