The Burning Crusade and Wrath of the Lich King sure did make the World of Warcraft universe much more worldlike, but that took quite too much time. Now that the playground really is large, more and more players seem to ignore the not most essential parts of it. To that issue, Cataclysm will bring some justice.
Flying around the brand new Azeroth will both grant a chance for the new players to see the rest of the world and remind the older player what the place used to be like. Blizzards brilliance goes with upgrading the classic instances with heroic mode, what a blast from the past for the Molten Core raider and the Deadmines hero. Man, if only there would be a chance to finally wield the legendary Ashbringer as its finest, World of Wacraft would totally win my hearth like the public beta did.
Goblins and Worgen. Well they might give the PVP grounds a bit more variance; "Damn, didn't see that goblin sneaking back there. Hordes used to be bigger!" And well, a mangy worgen warrior does seem cool.
All in all, I just can't wait!
