MacRumors posted a news story that Apple has released iOS 4.3 Beta to the developers

MacStories reports that Apple has seeded the first beta version of iOS 4.3 to developers. The iOS 4.3 beta is available in versions for iPad, iPhone 4 and 3GS, and third- and fourth-generation iPod touch, as well as a separate download for the new Apple TV. Consequently, it appears that Apple will no longer be supporting the iPhone 3G and second-generation iPod touch with operating system update

  Apple Seeds iOS 4.3 Beta to Developers: Personal Hotspot, AirPlay Video Streaming, New iPad Gestures