The awesome guy at swgeek was kind enough to build a Flash 11.5/AIR 3.5 capable Flex SDK. You just have to install this SDK and you're ready to go for projects targeting the new APIs provided by this new Flash releases.
This Flex SDK can be downloaded directly on their site:
Combined version of the Flex 4.6 and AIR 3.5 SDK for the lazy ones on swfgeek.