They switched the Flash runtimes to a quarterly release schedule semi-recently. As mentioned in the roadmap document, the release that will include workers is coming in the second half of 2012. Maybe as early as six months from now, if you assume that 11.2 is coming very soon.
Keyboard input support in full-screen mode
Improved audio support for working with low-latency audio
Ability to progressively stream textures for Stage 3D content
LZMA compression support for ByteArray
Frame label events
ActionScript workers (enables concurrent ActionScript execution on separate threads)
Support for advanced profiling
Support for more hardware-accelerated video cards (from 2005/2006) in order to expand availability of hardware accelerated content
Improved ActionScript performance when targeting Apple iOS (What the??? iOS???)
Performance index API to inform about performance capabilities of current environment
Release outside mouse event API
Refactoring and modernizing the current core Flash runtime code base
Work on the ActionScript Virtual Machine
Updates to the ActionScript language
Doesn't seem like there will be anything new that can not be currently albeit less efficiently.