There has been a lot of discusion lately on the future of Flex. Adobe has published some white papers to clarify their position. The future of Flex seemed a bit murky but the latest paper appears to be more promising, other than the fact about 65% of the words are marketing ramble that talks about what Flash did in the past. If you are interest in this topic, read the document entitled Adobe's view of Flex and its commitments to Flex in the future.
then scan forward to the Flash Runtimes Roadmap at
http://wwwimages.adobe.com/www.adobe.com/content/dam/Adobe/en/devnet/flashplatform/whitepapers/flash-runtimes-roadmap.pdf (skip forward to the top of page 3. That is where the content actually starts talking about the runtimes roadmap).