Cocoanetics has noticed something that's become apparent to most iOS developers already: with the advent of iOS 6 in a few weeks, Apple is essentially phasing out support for iOS on the iPhone 3G. Apple is slowly deprecating frameworks that iPhone 3G-compatible apps require from Xcode and app libraries, and the upcoming version of Xcode (4.5, currently in development) specifically states that it does not support armv6 devices or anything below iOS 4.3.
In other words, both the original iPhone and the iPhone 3G have become extremely difficult for iOS developers to support, and by the time iOS 6 rolls around this fall, there will be essentially no reason for devs to try and make sure their apps and games work on the older hardware. While it may be technically possible to maintain separate codebases for newer and older hardware (by running old versions of Xcode), even the largest developers won't have financial reasons to do so.
And the audience likely won't care much anyway. The number of people this affects grows smaller and smaller every day -- most phone contracts last about two years, which means it's been a few generations since the iPhone 3G was released in 2008. And there are a whole lot of new technologies for developers to take advantage of, including iCloud, Automatic Reference Counting, and Storyboard development, that make apps easier and quicker to develop and would never work with the older iPhone models anyway.
Apple's never been accused of sticking with a product for too long -- the company has a reputation for moving on to the newer and better as quickly as possible. For developers, the iPhone 3G is essentially being lowered into the ground for good. Of course, that doesn't mean consumers are obligated to dump them; the existing apps they run will still work.