I've been a Flex developer since it's first beta however many years ago. Today I just saw this response from Adobe: http://blogs.adobe.com/flex/2011/11/your-questions-about-flex.html
*Does Adobe recommend we use Flex or HTML5 for our enterprise application > development? > *In the long-term, *we believe HTML5 will be the best technology for > enterprise application development*. We also know that, currently, Flex > has clear benefits for large-scale client projects typically associated > with desktop application profiles. > Given our experiences innovating on Flex, we are extremely well positioned > to positively contribute to the advancement of HTML5 development, starting > with mobile applications. In fact, *many of the engineers and product > managers who worked on Flex SDK will be moving to work on our HTML efforts > *. We will continue making significant contributions to open web > technologies like WebKit & jQuery, advance the development of PhoneGap and > create new tools that solve the challenges developers face when building > applications with HTML5. Emphasis mine. If anyone has followed any game or application development where 'many members' of the team are switched to the next greatest thing, that normally means there are few maintenance developers for the existing product and not much new innovation to it. The company wants its best and brightest working on its future, not supporting its past. Combine that with the facts that Adobe bought PhoneGap and released Edge preview. It's not hard to put all these facts together and see that long term they want an IDE & framework for app development in HTML5. Perhaps Flex5 will be an HTML5 version of Flex as they start putting together html5 components Outside of "having to support IE6" why would you choose to start a project in Flex today?