The god's honest truth? The one that no-one likes to hear?
Too easy. Oh sure there's the whole Sarth 3 Drakes blah blah blah. It doesn't matter. The exclusivity, the elitism that went with raiding is gone. With everyone and their grandma running around in epic raid gear, with anyone regardless of individual ability capable of seeing all content in the game...as soon as you do, then what? Do it on hard mode? Most people don't care about a hard mode, or the noddy badge achievements that come with it. What mattered was that exclusivity, and the gear that came with it.
That's all history now. Whether or not you like that notion is up to you. Personally, I've always found it...unappealing. Even though, today, I'm the world's biggest wow noob/casual.
Now, a lot of people who fall more into the traditional gamer culture may leave as a result of this but I'm thinking, a lot more casuals will stay. Most of those 11 million people playing WoW? They're not gamers like you and me. They're just shlebs. Housewives. Car Salesmen. School bullies and cool college kids.
Since I returned to WoW - mainly to play with friends who don't seem to be online much anymore either (so the writing's probably on the wall, again), I've been one of those ultra casuals. My DK is still sitting on 76. I'm in no rush to 80. If I do Naxx ever, that'll be great, but I'll probably do it once and forget about it. I'm apathetic about it all. Whether I keep playing WoW or not, I don't give a crap anymore. Maybe I'll play EVE instead. Maybe I'll go back to Warhammer. I'll certainly try out Champions Online and The Old Republic. Who knows. All that I do know for sure is that WoW definitely isn't the game for me if I'm looking for something much more than casual lulz and hanging with mah homies. What WoW always did best, it does even better now. It's Facebook. It's Second Life with fireballs and swords. For that purposes, it's great. If you want real challenges with applicable rewards, though? Look elsewhere.
Personally, I think I'm going to be spending a lot more time in EVE soon. Painfully difficult to get anywhere, huge and intimidating, but that's exactly what I liked about old WoW. I suspect we'll start seeing a lot of WoW-hardcore bleedoff to EVE, especially since the whole Apocrypha plus retail-box release coincided so perfectly with the current feeling of malaise within the WoW raiding community. The fact that it looks amazing on even a mediocre rig, and plays incredibly well even on a crap line, are two big bonuses for us SA folks too.