Well, since Alpha must be shorter, zones have to be more or less complete (even if they won't open for testing everything at once).
For sure in Legion Dalaran was second thing we got in Alpha (after DH starting zone), most Artifact/Order Hall started here after all. But in DF I have feeling that entering capital will be rather ending, not starting point for campaign (for mains, 'threads of fate' will for sure start here).