There are a few things that can lead to a downward turn in WoW's numbers:
1). The recession: With the global economy in a downward spiral, people are going to have less disposable income. With less disposable income, families are going to start cutting unnecessary or frivilous expenses...and nothing says "unnecessary or frivilous" like World of Warcraft. A lot of the younger players, those who do not pay for subscriptions with their own funds, will be dropping like flies.
2). Time: As time goes on, fads fade away. While it might not seem like one, WoW is a fad. As it's user base grows older, some will realize what a waste of their time it is. They'll find better things to do with their ample time.
3). Repetition: As often as fans tell me that there is so much variety to WoW, it's not true. The game is basically the same crap over and over again. Once you hit the level cap, there's really not that much more in the way of excitement left. Players will start to get bored, and will start to leave.
All this having been said, I think it will take a long time before WoW "dies".
1). The recession: With the global economy in a downward spiral, people are going to have less disposable income. With less disposable income, families are going to start cutting unnecessary or frivilous expenses...and nothing says "unnecessary or frivilous" like World of Warcraft. A lot of the younger players, those who do not pay for subscriptions with their own funds, will be dropping like flies.
2). Time: As time goes on, fads fade away. While it might not seem like one, WoW is a fad. As it's user base grows older, some will realize what a waste of their time it is. They'll find better things to do with their ample time.
3). Repetition: As often as fans tell me that there is so much variety to WoW, it's not true. The game is basically the same crap over and over again. Once you hit the level cap, there's really not that much more in the way of excitement left. Players will start to get bored, and will start to leave.
All this having been said, I think it will take a long time before WoW "dies".