This is what The Team has to say on their progress with ultrasn0w:
We’re fine-tuning the payload to make it as quick to load as possible (and making sure it remains crash-free of course!).That last bit is really important, because only the official @ultrasn0w and @iphone_dev Twitter accounts will be used to announce the official launch of ultrasn0w for iPhone 4.
As usual before a public release, there are lots of fake
The reason the unlock is taking a bit longer to hit official release status this time around is because the iPhone 4 uses a new baseband modem firmware – the baseband is the cellular
We’ve already seen The Dev Team showing off their jailbreak and unlock solutions for the iPhone 4, so it’s really only a matter of time before we get an official release. By the looks of it, we probably won’t have to wait too long to unlock our new Apple phones at this point.