They came from WoW to WAR, and before WoW they came from any number of games (that are only mentioned for MMO cred, if they were indeed old enough to play something before WoW.)
You can already see the posts coming:
a) "This game actually sucks."
b) "I realize now that this game isn't the second coming."
They will blame their boredom on the game, of course, instead of the fact that they not only obsessed over the game, but over every detail about the game before it came out.
Also, they will not recognize the pattern that goes like this:
a) Say "There's a new game in development, it looks like it might have meaningful PVP."
b) Collect screen-shots, make forum posts discussing possible game-play mechanics.
c) Write blogs about the upcoming game, and how it might fulfill something that has been missing from their gaming life (which is what WoW actually did, but they would save the "Hey, I returned to WoW" posts for later.)
d) Play the game obsessively when it comes out, write about it, form guilds, play it so much that the entirety of the game has been exposed (if not conquered) within a few months.
e) Get bored, blame the game, and move onto the next one that isn't WoW, because WoW is for wussies (but play it in secret.)
Whenever those players leave, the game will see it's true "hardcore" base. The term should be reserved not for those that play a certain style game in a certain style of play, but for those subscribers that stick with a game through thick and thin, ups and downs, waves of bored players looking for that next (non-WoW) thrill, because WoW is for wussies.
Now, if I could only BUY the game and get in.
I'll give it a few more weeks...the signs are there, but a lot of these players hold on until no one is looking. Hurry up, guys, I wanna' play without finding myself a victim of your boredom ("Hey! Someone new logged on! KILL THEM!")