With modern i mean the acctual new style, dungeon and raid finder were a big evolution from the oldschool but nowdays even those are getting old and the modern mmos are focused mostly on solo online content, the biggest examples are Final Fantasy 14, Guild Wars 2 and Elder Scrolls Online but basically all of the mmos now follow this route, Wildstar tried to go oldschool and got knocked out within a few weeks. Modern MMO style means that on the one hand there is active community between the players like all games now anyway (even the non-mmos and single players have online community now, chats etc) but on the other hand the content progression and obtaining gear can be done just by yourself without depending on the others.
To be more specific, the modern mmos are focused mostly on solo story content while at the same time there is the same online interaction that the previous mmos had - you don't feel alone. Raids do not play a big role in getting gear, they are just big events with multiple NPCs that fight the bosses and you can basically solo them without the need of other players, sometimes there might be more players there if they are open raids but working on their own. Dungeons have become the endgame content instead - 4 up to 5 man but even these dungeons you can choose to play them solo and maybe meet with other players too while they try to do the dungeon aswell but not that you need them in order to join and complete it.
I think that WoW will eventually be forced to follow this route, it doesn't have to do anything with the number of subscribers but because it's current system is getting really old and does not fit now, especially the big 20-25 and 10 man raids raids they belong in the past, not the raids themselves but the grouping system.