I'm going to assume, given the silence of everyone from Adobe (I know, they don't need to monitor this list, they do it on their off-hours, I understand), that this is not a direction that Adobe is going anymore and I'll try focusing on Edge or other HTML solution.
Sorry, missed this email.
The Flex Roadmap: http://www.adobe.com/devnet/flex/whitepapers/roadmap.html says that you can get support for FlashBuilder for a few more years.
You are invited to look at Adobe's HTML offerings, but you should know that the Apache Flex community continues to work on both the Flex that you know, and a next-generation version that can both with and without Flash. Apache isn't currently planning to develop IDEs per-se, but the current prototype of FlexJS allows you to use FlashBuilder, and I hope to see IntelliJ and others to eventually support it.
For more on FlexJS, see: https://cwiki.apache.org/confluence/display/FLEX/Alex%27sFlexJSPrototype
Thanks much, Alex