just cause these top guilds are quiting doesnt mean its the death of something. i honestly thing they are quiting because the content just isnt as challenging as it use to be, so its now just boring and repetative.
diablo 3 will have little to no effect on WoW, its not a pay per month game, and most of the people who will be playing, already play wow and have agreed to the annual commitment. diablo 3 isnt a MMO, there will be a 4 to 8 player cap per diablo 3 game(Server), no one currently knows the release date cap, BUT CURRENTLY the cap is set at 4 players per game.
the auction house is a gainer for blizzard and battle.net but i dont think it will be able to generate enough of a steam roll to create any kind of real profit. it may just cover the cost of the maintance of the game itself.
sure diablo 3 will be popular but peopel who want to raid will stick with WoW, which is a very very LARGE chunk of the wow community that plays now. Diablo 3 has (raids) like epic fights and what not but imo it will be just like a freakin heroic dungeon with like 4 people, thats not awesome, thats kinda like ehhh find for a game like diablo. if they wanted to make diablo 3 sucessfull and amazing they would create servers just like WoW, with thousands of players on 1 server, but i highly doubt they will from what ive read from beta testers and blue posts by blizzard. its all speculation now, but when i read about the speculation about the wow expansions its all about the same, alot of the speculation ive read in the past about the new WoW and upcomming patches and what not have been i want to say almost 85% true most of the time.