Dual-Spec capability is coming...

From Blizzcon 2008 (website found here):

People get passionate about the World of Warcraft classes they play -- which is why this panel is always one of the most packed and energetic every year. The developers began by focusing on the death knight’s design and followed up by explaining changes to existing classes to increase group flexibility (the developers' goal is for groups to be able to "bring the player, not the class"). Cheers erupted for the upcoming dual-spec system, which is being designed so players will be able to switch between PVP and raiding specs, for example, without having to untrain their talents. After the panel was over, attendees had more questions than the developers had time to answer -- but they'll get another chance at a second class panel and an open Q and A session on Saturday.