First I will say don't be fooled by the PR when they say more than 5 million players. That is just registered accounts to the game not active subs. It's not more popular then WoW and i can't say for Blade and Soul because they haven't said how many people are playing at this current moment. I can say when I play Blade and Soul I see more people around compared to Final Fantasy in different zones with each zone having multiple channels so i think that is a good sign that quite a few people play Blade and Soul (channels can hold quite a few people in it).
Right now Blade and Soul feels more alive than Final Fantasy XIV at this current moment too be honest i consistently see new players in starter zones high levels in multiple zones and this is only one server and its not a high population one. People believe that Blade and Soul failed but in reality it didn't. I see so many people playing it, streaming and watching it so people have a interest in it no offence but sounds more like salty people who believe their game is the best.
If I have to be honest with you currently at this moment there isn't that many people online on Final Fantasy XIV, but a patch is coming out next week so the amount of people you see online will go up but then after a few weeks it will go down again. New players do come into FFXIV in my opinion I don't see that many of them and i go into main city areas often maybe its just the time i play? I don't know.
Also about Black Desert Online most people don't know that game has no end-game. When it releases people will not play it all that much. People just hype it up because of how good it looks.
Just to say you may get some bias opinions so i don't think things will be accurate. Final Fantasy XIV is popular as a P2P mmo (even though there are hardly any left so isn't much competition except for WoW) and there are people playing it but recently people have begun slowly drifting away due to the same content cycle which some got bored off.