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.
Ha! Been asking for this feature for the last 2 years. Now it's just 3 releases away. What's that like...2 more years?