iPhone hacker P0sixNinja just posted an update on Twitter saying his GreenPois0n jailbreak should be updated to support the recently released iOS 4.2.1 within a few days. According to his words, the jailbreak will be tethered or semitethered, whatever that means.

Earlier today, the Dev Team also gave us an update about the iOS 4.2.1 jailbreak and unlock saying they were working hard on it. Things look pretty good and it seems everyone will be able to get a jailbreak relatively soon. Older devices like the iPhone 3G and 3GS will most likely even be untethered and unlockable…

I want to remind you that as usual, if you rely on an unlock for your iPhone, you should not update to iOS 4.2.1 just yet. PwnageTool is always the preferred method to update.