Ok. I lied. WoW is not dead. Recent reports from Activision financial states subs are down to 9 million, that was the number WoW reached in 2007.
That was 5 years ago.
So why should WoW suddenly die. They got more subs than any other subscription competitors combined. They lost more subscribers than most competitors ever had lifetimes. And its normal. Pre expansion WoW always declines a bit. Wait until Pandas invade WoW and you see them all back "checking out the Kung Fu Pandas".
WoW is now old but still rocking. I don't see WoW vanishing for the next 5 years minimum. Reason is simple: most successful MMO's are still around. Even Ultima Online is still there and rocking on its scale. So don#t worry, WoW is a stable environment where you can invest your time.
Even if Guildwars2 had to stop digital sales as their servers became too full. Threatening WoW takes much more than a good game these days.