Look at it this way, using your logic that year one was a beta test; That means every expansion in WoW was a beta to the next expansions, or each call of duty was a beta to the next one. It's just the natural process that a game goes through. Dev makes game -> we play game -> devs make expantion/ (or next in that series of game) changes based on what we want while creating new content or expanding story line-> we buy expansion and so on and so forth. Common misconception is that this is just another dlc however with the progress of the story and amount of content this would be an expansion not a typical dlc. This is more like the burning Crusades to vanilla WoW.