Finally, even though its not official, iOS 4 is set to work on iPhone 2G. The new project by a group of hackers called whited00r project enables the iPhone 2G owners to run the modded iOS 3.1.3 on their handsets. You can find my previous post, which stated the features of the iOS 4 on iPhone 2G. The installation guide for iOS 4 on iPhone 2G is here: whited00r.
Im yet to try this out since I’ve gotta use my phone 24×7. :D. Will try out in my friend’s phone very soon! :). You can find more information about the project here: The Whited00r Project