I feel like people aren't necessarily interested in replaying classic WoW for the content but more for HOW the content played. Playing through the same dungeons, raids, etc. as they did 14 years ago will be a hollow experience. But if they (or someone) created an MMORPG around Starcraft or another popular franchise, it'd be a golden opportunity for Blizzard to apply what they've learned from WoW over the past decade.
I actually think another top-tier MMORPG is inevitable. The other half-assed ones, including WoW, all need to go away first, though, and the new title needs to be one that somehow applies to huge age demographic ranges. From teens to 40+. Which kinda sucks because millenials have grown up on ezmode basically and like their games dumbed down to the point where you barely have to play them.