Blizzard announced the release for WoD as 11/13/14 at an event this morning, along with the cinematic and a couple extra videos which are embedded below for laziness. A couple announcements for the pre-expansion event were also made today:
There will be a pre-expansion event in Blasted Lands where you push the Iron Horde back through the dark portal. You can test this on the beta by going through a portal in Org (and I assume SW as well).
You will be able to run the updated version of UBRS at level 90 as part of the pre-expansion event, similar to how we got to do the Theramore scenario at level 85 before MoP released.
These will both be released with or after 6.0, which probably won't be released very soon because Blizzard literally just started balancing things on the Beta.
It seems like they shoot for the pre-expansion content patch being released 4 weeks prior to the expansion (see below). Exceptions are for BC which was delayed, and Cata which involved removing/updating a large amount of existing content. In this case, they might try to squeeze it out sooner since the last content patch (5.4) was released over 11 months ago.
