https://www.youtube.com/watch?v=qhNkK4h1oVk&feature=youtu.be At the 1:00 mark they said all that land will be playable. Its not, and will not for the release. They said only one zone per planet.
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If you've played or seen wow, each continent is one playable zone. And they are -blam!-ing huge. One playable zone just means you can walk from one side of it to the other, that doesn't mean it's small.