Given that FFXIV is on 1st position right now
https://mmo-population.com/activity
I hope AoC will stay on 40 to avoid attracting voices who want fast travel and all no risk activities.
That website says WoW is at the top. It also includes non-MMOs.
Though, those population numbers are all pathetic, especially compared to WoW's 12 million peak. If anything, I think that proves that MMORPGs are a dying genre. This is one of the reasons *not* to follow modern MMO trends. You could argue that "the current MMO market wants and expects X, Y and Z," but that's ignoring the fact that this market is heavily on the decline and approaching death.
If you want your new MMO to be a big success, it should strive to be more than just "another one."