Because there’s no 4.3 beta for iPhone3G, it’s effectively unlocked for life via the 06.15 ultrasn0w unlock
However, here is the bad news. This means that iPhone 3G users will not get the iOS 4.3 update and will possibly be locked out of any future updates coming from Apple too.
The iPhone 3G was launched around 3 years ago, so it makes sense for Apple to remove support for the device considering that they might launch the iPhone 5 this year.
So have fun with your unlocked for life iPhone 3G but don’t expect any new goodies from Apple.