At the moment it's been peaking at 3000 online. Which is pretty much what it was years back. Isn't that what a MMORPG is about though?
With established streamers promoting FFXI lately, there has been an increased interest too.
The problem is not the numbers of players but the fact that, as most content is in a limited amount of areas now - There needs to be more instances added for battlefields, and more Apex monsters on Asura.