A recent interview with Rob Pardo at E3 by the OC Register reveals little we don't already know, but does suggest that Zul'Aman will be about half as large as Karazhan. Blizzard has taken complaints about the length of their only 10 man dungeon to heart, perhaps mirroring the length of the comparable 20 mans from pre-BC such as Zul'Gurub and the Ruins of Ahn'Qiraj.

More information about Blizzard's next dungeon, Zul'Aman, can be found here.