The folks over at Open Source @ Adobe have begun discussing Flex 4, code named Gumbo.  Matt Chotin has a presentation on the roadmap for the product as well a distilled set of features.  Ely Greenfeild also has a video up showing how MXML will be used to simplify skinning.  The scheduled release date isn’t until the 2nd half of 2009, but it has promise to be an exciting release.  If you have time, stop by and check it out.