According to a new 'blue tracker' post on the World of Warcraft forums, the faction-based auction house system will end with v6.0 and result in a unified auction house between Horde and Alliance.
Yes, in 6.0 auction houses are unified between factions on a given server. The benefit you cite is a major reason behind the change.
Posted by Verrazano
Hopefully it is. It would make life a lot more bearable as minority faction on an unbalanced server.
Read more in the discussion thread on the World of Warcraft forum.