Any other source (Steam or looking at how many have completed this or that on console) are just guesses.
Lag is ruinin' my 'mershun! A society grows great when old men plant trees whose shade they know they shall never sit in. There is only one good, knowledge, and one evil, ignorance - Socrates Member of the Old Guard, keepers of the game's history
I see lots and lots of people roaming through Orsinium. So far there's no problem getting people for world bosses, etc. Zenimax won't share numbers, but it seems to me there are more people on more often with Orsinium then before. Populations run in cycles.
"We have found a cave, but I don't think there are warm fires and friendly faces inside."