Thibault Imbert, Flash Player Product Manager at Adobe, has now confirmed that Advanced Echo Cancellation (AEC) is coming to Flash next year. Thibault stated in this JIRA ticket:
"Hi guys,
Yes, AEC is coming and you saw it in the docs ;)
It is implemented and tested, and available soon. I cannot give you a date for now, but it will be next year.
Thibault"

That's great news and it confirms what some of us have been hearing for some time. The docs for AEC and a new class called a href="http://help.adobe.com/en_US/FlashPlatform/beta/reference/actionscript/3/flash/media/MicrophoneEnhancedMode.html" target=_blank">MicrophoneEnhancedMode are already available but AEC is not yet part of the current 10.2 beta drop of Flash Player which is now up on labs.