I may not have the experience to speak about it but in 2 short years I've seen the trend. WoW was my first MMO and my very first RPG game of any kind.
I do know that there are a ton of new MMOs coming out this year. However, from my experience with WoW I've noticed things take a turn for the worst or better depending on your view of things. I've started playing WoW during WTLK and according to me it still had a certain element of exploration, meeting people and working as a group. Even though I wasn't a hardcore raider I was happy running my Heroics cause I went out of my comfort zone to find players and meet new people to form a group. With the dawn of the LFD Feature, Heroics didn't really feel an "epic" adventure any more.
I soon realized with time, that to really succeed in an MMO compared to any other Genre you really have to invest a considerable amount of time in the game. And most MMOs follow a similar design philosophy where you grind your way to high level. I think what we really need is something revolutionary when it comes to design.
The people of my generation just don't have the patience to grind it out and are only in it for "immediate results or satisfaction". At the same time some people don't have the hours to commit to a single game especially one that can take hours in a week. The game developers are picking up on the trend and are coming up with ways that can keep hold of the casuals. The Challenge Mode in MOP has Activision all over it. You get Medals, etc for completing the dungeon in a certain time? Isn't this suppose to be World of Warcraft and not some military shooter game?
I don't really think you can call WoW a traditional MMORPG in its current state. It is more of a MMOG game. The "role playing" has been removed and the immersive factor has been removed. It now is nothing more than a lobby for smaller mini games. To keep it profitable Blizzard are trying to change everything and appeal to a different demographic - The Casuals ( I DO NOT MEAN BADS)
I was surprised when a friend said that SWTOR didn't have a LFD, but how long before Bio Ware is forced to play that card to keep up subscription numbers when people keep crying for one.
Guild Wars 2 from what I have read seem to be changing the landscape here from what I have read. On the other hand Skyrim showed us in the age where "multi player games" are highly popular that you can still come out highly successful if you truly have a good and engaging game RPG. I do see the future where RPGs introduce a co-op mode where you can play with upto 4-8 people.