It’s the end of further iOS development for iPhone 3G. Via 9 to 5 Mac:
What’s missing from the iOS 4.3 beta page? Downloads for the iPhone 3G and iPod touch 2G. It looks like iOS 4.2.1 is the final release for Apple’s second generation iOS devices. Oy.
This brings an end to further development of iOS support for the second-generation iPhone. The previous release, 4.2.1, improved performance on the device after version 4.0.1 caused significant slowdown on that older model.
Time for an upgrade!