Dark Eldar are being confirmed by the latest 40k Radio Podcast, for a pre-order date of September 20th, and full release the weekend after. Definitely hoping for more than a single release, and getting the appropriate amount of funds pointing in the right direction for this release.
Please remember that this is ultimately still a rumor. I have yet to sit down and listen to the latest podcast, but will try tonight. Here is a link for you to listen to the latest from 40k Radio.
http://www.40kradio.com/
via a reader on Faeit 212
Just listened to this weeks 40K Radio podcast - and they mention briefly that Dark Eldar are confirmed for pre-release next weekend (20th) and release in two weekends (27th).
They follow it up with their usual caveat of "this is not a fact", but also joke that "everything that is not designated a fact is, ultimately, a fact".