The big question I have is will they add new content after 40 man Naxx like a 40 man Karazhan with better loot to keep the progression going or its all going to end with Naxx for eternity.
What was cool about classic is that you had very few guilds finishing all the content before new content was being pushed out. I think after a while when guilds have Naxx on farm they may release a new 40 man raid to keep people progressing.