yep, true.It's a odd topic to think about... what comes after wow? Do you make another mmo from the ip? You could though it is also was a ripe setting for almost any fantasy adventure game ( I would argue you would have to set it pre bfa though).
I don't think games that purposely waste your time doing trivial content will last long in today's market you can look at steams activity charts. You don't see cookie clickers in there.