It depends what you define MMO as. If you consider it as traditional MMORPG, then the answer is clearly yes. WoW once had 12 million active players, now FFXIV i

It depends what you define MMO as. If you consider it as traditional MMORPG, then the answer is clearly yes. WoW once had 12 million active players, now FFXIV is likely at 1.5 million, we're not sure if WoW is still above that, and ESO, SWTOR, GW2 and Runescape have a couple of hundred thousand each. If you extend the definition a bit you can sort of fit stuff like big minecraft networks, Path of Exile, etc. into it. Which initially seems a bit silly, but then people general consider things like retail WoW, Guild Wars 1 to be MMOs despite most gameplay taking place in explicit instances, or world zones that are so heavily instanced that you'll only see a small number of other players. And the gameplay of Path of Exile is hardly as disparate from WoW as say Eve Online or Runescape.