The iPhone 4 lock-screen exploit bug that allows anyone to access information on your iPhone even if you have a passlock enabled is hopefully going to be fixed with Apple 4.2 iOS update.
The team over at BGR have been trying to circumvent the security with the new 4.2 developer release installed on an iphone with no success. So it looks as if the security bug has now been fixed.
However Apple has made no official announcement when it will be releasing the new iOS 4.2 update into the public domain. But going on past experience its normally around a week after the update has been released to developers.