Actually, if you want to be very truthful about it, World of Warcraft has never been released "finished". Just look at the last expansion, WotLK. Ice Crown Citadel wasn't even in the the game when Wrath was released. You couldn't even fight the Lich King when it first game out and that was pinnacle of the expansion.
So really if you want to get right down to it, people were able to play Wrath they way it was released and people are able to play Civ5 the way it was released. Patches and updates opened up more in Wrath and so I'm confident that patches and updates will open up more of Civ5.