I don't play WoW anymore, but I have many friends that do. I can tell you from experience that what's happening now has happened before. Every time a big patch gets dropped, everyone panics, complains, threatens to quit the game forever, then, after a few weeks, they get used to it. A few months later, when the next big patch drops, it begins again.
This time next month, everything's likely to be back to normal. Well, as normal as the WoW community ever gets, anyway.
Take heed; as it is now, nothing can kill World of Warcraft. It's just too much of a behemoth with too much momentum behind it.