VR's potential strength when it comes to MMO's is about its immersion factor, not graphic fidelity. It's the MUD -> Graphical MUD levels of progression.
Think about the first time you fought Ragnaros and how god damn huge he was and how impressive it was that you were just a dinky little dude with your 39 buddies taking on an elemental lord 10 stories tall. Now think about that in VR for the first time, having to crane your neck to look up at his mace smashing down at you.
Think about riding on your mount to a dungeon and looking to your left to see your 4 buddies riding at your side.
Think about a shitty pull where half the dungeon is running at you and the VR aspect makes you panic because it feels like they're coming for you, not your character.
etc...
Sounds exhausting tbh. Craning my neck every-which-way to see my surroundings? That would get annoying quickly. It's a novelty.
Graphics assist with making a good game but first and foremost is always the content & story.
EQ drew people in due to graphics 1st, but they hooked you with the lore & gameplay.
I really don't see VR tech being mainstream for at least 20-50 years. There are so many problems with it right now:
1.) Motion Sickness
2.) Uncomfortable headsets
3.) Can't see your surroundings (IRL) - I like to know who's in the room with me / watch kids / talk to wife / etc.
4.) Visual Fatigue
5.) Physical Fatigue (Even if not physically moving around, you will still move your head/body more than when playing with standard mouse+KB).
6.) Tech burden - need large adaptation of high powered hardware - maybe phones can someday do it or a cloud-based game
7.) If the content sucks, you won't keep people playing just because of VR.
I see VR being used for sports games first. I can see VR Football, for example. Or a VR FPS game. Games with small teams and built for FPS style gameplay. MMOs are NOT fun in FPS perspective.
Any MMO VR game will probably lack in the high-end content we're accustomed to. It will do poorly with Raids, for example. Raids require a large overhead camera. If you're in an FPS perspective you're not going to have fun at all.
I could see an MMO VR game that is very sparsely populated, except for cities, maybe more of a gathering/crafting sim, a 1800s timepiece game of America. A western or Oregon trail type game. Or if futuristic, an exploration game like No Man's Sky, etc.
But a large scale grouping/raiding game.. not VR friendly at all