If you are still among the few people who own an iPhone 3G, then I inform you that your device will become completely irrelevant to developers as soon as iOS 6 it will be officially released and will have an updated version of Xcode. Apple has long since removed from Xcode the frameworks that are necessary for the applications to work on the iPhone 3G, and the Xcode for iOS 6 will remain completely without these frameworks and the development of applications compatible with iOS 6 will become impossible.
The iPhone 3G has been discontinued 2 years ago. But there is also a technical reason why 2012 will be the final nail in the coffin that buries the iPhone 3G: The deprecation of armv6. The discontinuation of support for armv6 has already been a year in the making. In Xcode 4.3 Apple had already removed the armv6 setting from the ARCHS_STANDARD_32_BIT, that was strike one. I argue by accident because at that time you still had to submit so-called "fat binaries" that have compiled code for armv6 and armv7 in the same file. From that point on you had to manually add the armv6 setting to the Architectures in Build Settings.
Xcode will no longer offer developers the opportunity to produce applications that support an iOS version lower than 4.3, and the iPhone 3G can only install iOS 4.2.1, so that's the end of the 3G's life. If you still own such a device, it would be advisable to sell it and buy a more recent iPhone model, otherwise you will no longer be able to use the new applications. Finally, I must note that the iPhone 3G is 4 years old and this decision is perfectly normal, considering that the development of applications compatible with such old systems is very difficult.
