MMO's and there current set-up

I have been up on playing WoW and have noticed that they are trying to switch from the generic Tank/Healer/ Dps roles and wanted to focus more on the ability to Crowd Control. i have heard from other mmo's that they have switched it up even more drastically. I like the current set up, i enjoy tanking and healing, but i've heard from others that this can get repetitive as a lot of those players have been playing since the open Beta, while i think its a good idea for a change, i think that the current set-up they have set-up the foundation for their game if they mess that up, they could lose all there old regular players.