There is no downfall in WOW.
It still has 9 million + paid subscriptions (per hour or per month).
That's an AWESOME amount of subscriptions compared to the rest.
The fact these numbers went from 12M to 9M are in 2 years time are:
1. WOW has been around for 8 years. That's extreme for a single video game.
2. ALL AAA subcription based MMo's went free to play. WOW KILLED all WOW killers.
3. World economy is in heavy recession and in some countries in depression (EC), world economy went down and video game suffered with at least -25%. The only subscription based games left are WOW and EVE the rest is sucking players dry with cash shops)./
4. WOW has now MORE options, MORE content, MORE choises of play, so in game issues were not the cause . Things like "we level too fast", ... "you can shut down experience" are just counter of counter arguments without relevance.
5. 10.000.000+ copies of Diablo 3 were sold, so expect MoP to go grow again, now that everyone saw D3 and GW2 (and its lack of features compared to WOW).
TLDR. Learn to view with a bigger angle OP.