"Unfortunately, this meant that shortly after Cataclysm's release the average player found himself confronted with a very trivial leveling game and very hardcore heroic dungeons that had often to be completed in an unpleasant social environment. And all this was necessary to start raiding which was rather hardcore and as such inaccessible for many of them.I do think that the trivial and too fast leveling experience has other reasons than those Nils mentions (Team B was following a Team A policy of time to level cap having to be a constant), but I do fully agree that trivializing the leveling game and making the endgame less accessible are the main reasons for the relative lack of success of Cataclysm.
The result was a 5% drop (after creative bookkeeping) in subscriber numbers shortly after Cataclysm had been released in Europe/NA and WotLK had been released in China."
Now I'm reasonably optimistic that Blizzard understands at least the raiding problem, as some of the devs' comments and actions suggest. Thus there is a chance that the next World of Warcraft expansion will manage raiding better, hopefully with a better system of variable difficulty which makes raiding accessible to the majority of players, while keeping is challenging for the more hardcore. I am much less optimistic that Blizzard can reverse the trivial leveling problem. Assuming the next expansion adds yet another 5 to 10 levels to the game, Blizzard would basically have to double the time to level cap to reach a speed in which people don't outlevel zones before consuming the zones' content. While this would improve the game enormously (even my ultra-casual wife complains about too fast leveling), it would be far too easy for the people who hate leveling to paint this move as a huge money-grabbing nerf. Thus there is some doubt whether Blizzard can reverse this mistake. With WoW not getting any younger, it is quite possible that future expansions will not be able to recover subscription numbers, and that WoW has peaked.