Blizzard recently had a fansite chat, they've posted a transcript of the chat on their website here (http://www.worldofwarcraft.com/misc/fansitechat/04-12-13.html).

Looks like linked auction houses are in the works:

We also plan on putting auction houses in all major cities and linking them to one another.

Discuss it here (http://wow.forums.thedruidsgrove.org/showthread.php?p=115781#post115781).