Prediction time:

1. BLU will be released to widespread adoption. It'll be new content in a period where people are content starved.

2. The class might see an initial downward tick in population, but it will be relatively minor. There are all manner of safeguards built into the experience to ensure retention. Eureka the job will have Eureka the grind built into it, I imagine the chance to learn monster spells will be lower than anticipated, and the bonus exp from world mobs will be relatively minor.

3. Then people reach the Carnival and here's where it gets interesting: this will be the height of Blue Mage talk and engagement. It's designed to be the height of the experience - and here is where it will fail. In short order, a number of days if not less, a full and complete guide to the Masked Carnival is released. I cannot see Square designing a niche solo experience with the complexity of 25 Savage Mode raids. Most fights will be primarily about finding and grinding for that perfect spell to counter it. Furthermore, we'll have guides which boil the entire experience down to a recipe-list. Sure, one could opt not to spoil the experience, but people as a whole will.

4. We will see the class numbers and engagement start to take a nosedive shortly after this. As the endgame BLU experience is turned into a checklist on Reddit and Square cannot keep up an endgame for everyone else and then the odd-kid out BLU's "custom content" quickly goes from Masked Carnival to Hidden Sideshow. There will be a trickle of content for it, but not enough to recover enthusiasm for the class nor enough to keep up with what everyone else is getting.

5. There be a tiny community of Blue Mages, just as there's a small community that enjoys Verminion or Chocobo Racing. To those people, from me, hats off. No, seriously - I enjoy the PvP in this game which as I understand it makes me a bit of an oddity. Tragically, though, for most Blue Mage will be a quaint and curious sidetrack, something to be entirely ignored or at best endured when the occasional bone gets tossed its way.

Let me sidetrack into another point. Let's say I'm wrong. BLU is popular and acclaimed. So, reasonably Square continues the experiment. In short order we have Defanged Beastmaster alongside Hamstrung Puppeteer added in future patches. Of course, they'll need their own sandboxes as well. Square goes from designing one endgame experience to two with Blue Mage . . . then 3 . . . then 4? Where does one draw the line? Even if they roll everyone into the Masked Carnival "setting" they all cannot fight the same battles - they need to be tailored and crafted to each Limited Job. Without designing two separate, parallel, and yet equal content pipelines how does one fulfill both communities? One side or the other will be left anemic in comparison.