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.

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="" 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.