Last fall, the working group responsible for designing the next version of ECMAScript released an overview of proposed features for ECMAScript 4. ActionScript is based on ECMAScript, so the hypothetical ActionScript 4.0 will undoubtedly support some, if not all, of the proposed features.
In February and April (in Amsterdam and Toronto, respectively), I'll be doing a lecture at FITC covering the ECMAScript 4 features that will theoretically be added to ActionScript 4.0.
Read my FITC lecture notes here:
>> http://moock.org/lectures/newInECMAScript4/
Get information about FITC here:
>> http://www.fitc.ca/