Correct me if my sources are wrong, but the only place where IMC has stated anything about the hidden classes limitations has been on the FTG Interview after the second closed beta, which is described on the following paragraph:
http://tos.nexon.com/community/free/view.aspx?n4ArticleSN=14515
히든 직업은 서버에서 몇명만 혹은 퀘스트상 특정 조건을 둔다던지 넣을거고 직업은 어떤 계통 1개 어떤 계통은 3개등 해당 계열당 적용되는 히든 클래스 수는 다를 수 있음
And the best translation we have is the one made by /u/emailboxu on reddit.
https://www.reddit.com/r/treeofsavior/comments/387kc2/full_ftg_interview/
We want hidden jobs only unlockable by a limited number of people per server, through quest rewards after meeting certain conditions.
Some hidden classes might max out at 1 Circle and others at 3.
I’m concerned about the interpretation of the hidden class limit, most of the people consider it to be that there will be a fixed numeric limit that will constraint the quantity of people that will be able to have access to a hidden class, even there are theories that this fixed number is linked to the player ladder… but bare with me for a second because I have another interpretation for that text.
To explain this, let’s go back and explain Ragnarok Online’s Guild system (I can feel some people starting to lift their pitchforks and torches, just bare with me for a sec ). To make a guild on RO, you first need to have an Emperium item, while the Emperium it’s actually a rare item (uncommon if your character is strong enough to farm orc skeletons), the fact that you need one to make a guild actually limits the ability to actually create a guild, so the only players who create guilds are the ones that play long enough so that they can get an Emperium on their hands and actually want to make a guild because of the emperium alternate uses.
You could say that if you could farm enough Emperiums, there wouldn’t be a limit of players who make guilds, but the actual case is that there are lot’s of people that haven’t even made a guild even after a year of playing the game. In the end, by adding a little game restriction they actually limited the quantity of people who were able to make guilds, i think that they were implying this kind of limitation when they said “We want hidden jobs only unlockable by a limited number of people per server, through quest rewards after meeting certain conditions”.
My interpretation might be wrong too, but at least it makes sense to me. Also, I actually don’t dislike the other interpretation since it would add a bit of competition to the game, which is something that is lacking on most MMO nowadays :p. But in the end, nothing is written in stone in this moment, so we can have fun theorizing xD