There are posts and rumors about iPhone 4 Jailbreak but there is none so far. The jailbreakers are not ready to release even though some have the tools, like Goehot who seem to have a new exploit called “pwned4life” which can jailbreak and unlock all iPhones for life is busy watching World Cup 2010, but the USA is out of the tournament and he might start work on it.
There is no iPhone 4 or 3GS on the new bootrom (meaning a 3GS running 3.1.3 jailbroken with Spirit) JUST YET. Progress has been made, but there is no public jailbreak. The Dev-team has gotten root access using a userland jailbreak method. There is no "the userland jailbreak method," it's a general term.iPhone 4 Unlock is something entirely different, if you read the article "PwnageTool 4.01 Released,",
There is NO RELEASE DATE. We might not see a public release jailbreak any time soon. Could be days, could be weeks. Also can depend on if Apple patches iOS 4 to work on any issues like the antenna/signal issues (possibly Monday, but no one knows for sure.) Releasing a jailbreak now means Apple will probably fix the exploit on the next patch, and since the antenna issue may be serious and quickly fixed, the Dev-team will not waste a jailbreak method and end up having a must-have/quick release patch break it in a few days. through digg user Brak710101
You know that the iPhone Dev Team already released ultrasn0w 0.93 for unlocking your new iOS 4. Anyone wants could do this by simply adding the "Cydia repo: repo666.ultrasn0w.com". The current version of ultrasn0w will unlock basebands 04.26.08 thru 05.13.04. If your unsure, that means that ultrasn0w unlocks ALL basebands since iPhone OS 3.1. Even more specifically, 04.26.08, 05.11.07, 05.15.01, and 05.13.04. Remember to disable 3G on T-Mobile USA.
So there it is now. But before doing anything, unlocking the iPhone 4 or Jailbreaking the iPhone 4, which might simply break the iPhone 4, wait a little. Apple is certain to release a new fixes soon as they are finding a bunch of bugs and then there is iPhone 4 Antennae issue. Just admire the new phone for a few days and carry your of phone around. Also checkout this live Cydia App compatibility list.
More info: iPhone Dev-Team