Over the past 24 hours or so, word has gotten out that the next major version of Flex Builder, currently codenamed "Gumbo", won't be named Flex Builder, the final product name will be Flash Builder 4. This is a good thing, it'll greatly simplify explaining the Flex/Flash relationship, an obstacle that we still deal with every time we present Flex. So, the Eclipse based tool will be named Flash Builder, emphasizing that it is used to build apps for the Flash Platform. The Flex framework will still use the name Flex, as will the Flex SDK. This greatly clarifies what Flex actually is, Flex is an ActionScript 3 framework for creating apps for the Flash Platform. It's nice and clean, you can use Flash Builder and/or Flash Professional to build apps for the Flash platform, and when doing so you can start from scratch or you can use the Flex framework (which makes you a Flex developer, so you are free to still call yourself one).
For more on the subject, Tim Buntel has posted his thoughts, as has Lee Brimelow (who also posted a FAQ), Serge Jespers, and Duane Nickull.
