We know that patch 2.4 removes the attunements for Mount Hyjal and the Black Temple. And apparently the access to the new Sunwell Plateau raid dungeon is opened by a world event, not an individual attunement. That would mean that from all the level 70 raid dungeons only Karazhan would still have an attunement. Why?
I could understand a system where access to the first raid dungeon is easy, but an attunement prevents people to move on to further raid dungeons before having finished the first one. "Bring me the head of the prince before you can enter Serpentshrine Cavern", no problem. But why, oh why, would somebody design a system which keeps people out from the start but then lets them go anywhere?
Now somebody is going to say "but you can't just go anywhere, because the Black Temple is tough". But doesn't exactly the same argument hold true for Karazhan? You can't go to Karazhan with a group consisting only of people who just dinged 70 and are dressed in greens, it's too tough. What sense does it make that a guild can drag a noob through Zul'aman or a 25-man dungeon with the help of 24 well equipped people and thus equip him with epics, but they can't take him to Karazhan unless they help him with the attunement dungeons first?