Preview at WWDC likely in June, followed by September launch.
iPhone Passcode Flaw Already Addressed for Future Firmware Update? [Update]
The workaround allows unauthorized individuals access to the iPhone's Safari, Contacts list, SMS, Maps, and Mail.
MacRumors has been told that this security flaw was already reported to Apple earlier this month and has been acknowledged as an issue. A fix will presumably be included in a future firmware update.
Update: A simple fix is available in the meanwhile. Users should set their "Home Button" double-click preference to "Home" or "iPod" rather than the default "iPhone Favorites".