"As for full on sub numbers nobody knows them but right now 3-4 million is probably a massive highball." The tiniest bit of research would tell you that it is wrong. Legion is doing better than WoD, they say that every single earnings report, and they aren't referring to WoW at it's low point, they are referring to it at a similar timeframe (q2 for q2)
So, Legion does not have under 5 million subs, that is a ridiculous thought with no backing other than "WOD WENT LOW, THAT MEANS EVERTHING LOW" WoD had such low subs because it had absolutely nothing and even when it did hit 5.5 million subs, that was during a drought, right now there are still Argus subs and expansion resubs. Legion likely stabilized at 6-8 million for the majority of it's life cycle. It had a better theme and a wider reach than MoP, which more content, and more re playable content than either of the last two expansions.
But let's assume that WoW does have 4 million subs. That would still put it above FFXIV, which player projected estimations were anywhere from 800k to 3 million.
Guild Wars 2 profits have been on a sharp decline lately and I doubt Path of Fire was enough to bring it back to WoW or FFXIVs level.
ESO only went up during the Morrowind announcement and after the disappointment that was the playerbase slowly trickled down to respectable but not WoW (or FF) levels.
The only mmorpg on the market right now that can even try to claim a similar number of subscribers or active monthly players (which 7.3 did see an increase in according to financials) is Final Fantasy, but it is generally not even disputed by their community that WoW is still leading the pack, especially considering Legion did so well with content relevancy.