I really doubt that they would make Bozja mandatory for future storylines about Dalmasca. They took a long time to even make something like the crystal towers mandatory and you can do those in one evening if you watch the cutscenes fast. Even if they nerf Bozja to the ground you would still need a much much longer time to finish it all, including having to wait and hope for castrum and the new instance. I also doubt that they would continue this story with the next relic because that would mean that people have to do old relic content to start the new one which is a bit much.

Honestly for me it makes the most sense that they will explain this stuff in the story quest and we may or may not get a few reactions from some of the bozja NPCs.