I've stopped playing WoW just after Christmas, because Blizzard are targetting a different demographic these days:
Pandas, Pokemon pets, foolproof talent, gear, gemming choices, simplified
everything. It is no longer interesting enough to theorycraft for, and the huge influx of children with short attention spans drove so many of the serious players away.
I could be wrong, but I suspect WoW is irrepairably damaged and a lot of serious players are either taking a break from MMO's (like me) or waiting eagerly for The Next Big Thing(TM).
Moving servers will just delay the inevitable; my guild moved off a dying server and the problem just happened again three months later.
The game has stagnated, people are tired of something that has been milked too hard, and it and it's hemorrhaging players now as fast as it accrued them in the first place.
If you look at subcription figures (
http://mmodata.blogspot.co.uk/) then you'll see that WoW peaked at WotLK, slumped quickly with a brief spike for Cataclysm, and has continued to lose players since then. The temporary respite in the falling numbers can be attributed to the "subscribe for 12 months, get DiabloIII free" Around 30 people in our guild took up this deal, and only a couple of them still play WoW.
The real proof is that the number of servers with active, healthy populations is falling fast. The vote to move our guild again failed, because it costs money and because there's absolutely no guarantee that an active server will stay active.