Apple has released the update for iOS4. iOS 4.0.2 update patches the PDF exploit used by JailbreakME software (developed by iPhone Dev team).
You can update your iPhone/iPod Touch with the new software, however it will not be jailbreakable as hackers haven’t yet found an exploit in this new version of IOS4. However if you are still interested in updating to the software you can do that through iTunes. Next time you connect your iPhone/iPod Touch you will see a message in iTunes that allows you to update your phone.
Shortly after the update got released, there were reports regarding some devices still being jailbroken. For now Apple iPhone 3G and non-MC models of iPod Touch 2G are still jailbreakable on iOS4.0.2 using the latest version of Redsnow. You can also unlock the iPhone 3G on iOS4.0.2 since the update does not make any changes to the baseband.
Apart from iOS4.0.2 update, Apple has also released iOS3.2.2 update for the Apple iPad. The update patches the PDF exploit for JailbreakME so if you can’t live with legit softwares its best to avoid this update for now.