Will Beastmaster appear in any Endwalker content patches?

[Auryan]

Would you be fine with a full version of blue mage if what blue mage is currently was left as is and continued to be updated as planned?

Sure. But that's unrealistic in a having-your-cake-and-eating-it-too kind of way. That it's possible to go that route, sure, but is it practical and worth investing more resources into what is clearly meant as strictly side content? No, not really.
If they're going to even attempt to, why not simply create a BLU-like mage that is similar, but doesn't have all the hang-ups? A Catmancer that has cats use a select few curated, synergistic monster abilities by feeding them treats. It's BLU/BST-esque, doesn't have much or any attention on learning these abilities besides on level and is distinct enough from the other mages.

Kind of what Archwizard mentioned a while back.

EDIT: changed for more clarity