I don't think they're going to do another one. A job you can't even use in duty finder content outside of undersized parties isn't really worth the amount of effort they had to put in to make it.
I honestly think we're going to see them do maybe one more small update to BLU and then quietly retire it.
I don't know how much effort it really took though. They had to do a few animations for the class but not a large amount since all spells are cast only in a few ways, all the particles are simply the monster skills so that was just a matter of resizing/adjusting positions, the class only has one set of armor unique to it and like 3weapons, so that part's fine too, then you have the unique content, which is a very basic arena(I wanna say it's a reused arena, but not entirely sure, still it's very barren so wouldn't take long to make) where you fight monsters that already existed. The only new model is the last boss in there.
They had to make some new UI stuff and design the various fights and quests still, but honestly when it comes to side content, it seems a lot easier than some other stuff they've done, like PotD/HoH/Gold Saucer/Vermillion and such, all of which have way more original assets, and due to its limited factor and theme, even though it's a whole new class, it probably took a fraction of the effort they need when they make a "real" class.
Now if they make say, Puppetmaster, that'd require a lot more assets, for the actual puppet and the various settings they can have and such, so I don't know if they'll do another, but I don't think BLU was particularily taxing.