The latest beta build has brought a new twist to the good old map interface. As MMO Champion reports, there is now a dropdown box on the map screen, letting you choose from a few different "floors." What this means exactly, we aren't sure -- the obvious conclusion is that you'll now be able to look at different sections of the world map (for example, see into different levels of buildings or caverns). And Dalaran (which this map is a part of) is one of those areas that has two different levels, so this particular menu will let you see both halves of the city.
But this also suggests an even bigger change: including maps of instances in the official interface. Since launch, Blizzard hasn't ever shown us ingame instance maps (though we're not sure why -- maybe they want to require players to explore instances rather than follow a map through them). But lately, addons like Atlas have made them easily available to players, so maybe Blizzard has decided it's time to map out dungeons as well. We'll have to see what use they put this new dropdown to.