Bozja is one of the largest successful pieces of content within in Final Fantasy XIV. I would compare its success equivalent to the introduction of Ultimate Raids. with the success of Bozja I am more excited to see how they will continue forward with the zones such as Bozja and even more Eureka like zones.
While I have enjoyed Bozja and believe that it was very well made content within FFXIV, I believe that it is hard to continue Bozja until they release the next area in patch 5.4. Part of this is due to to the reward system after finishing the story in Bozja. While you do feel accomplished and successful for completing the castrum in Bozja, Bozja feels underwhelming once you finished it. There are of course grinds to get Bozjan gear, which provide haste for within Bozja, or the clusters to farm to retrieve the new items, and even the Duels where you can work your way to getting new mounts. While these are great additions most if not all of these can be achieved during your grind up to rank 15 of Bozja. These grinds, while they are necessities for post story content, are part of which bores me at the end of Bozja.
While it could be my own bias, When I was in Eureka I never felt that grinding in eureka was as boring and bland and could always be repeatable. While yes Eureka was bad (I mean Pagos was god awful), grinding in eureka made me feel like the grind was worth it in the end (even if the eureka weapons looked awful). I always felt accomplished in finishing a portion of Eureka, whether that was finishing Anemos, Pagos, Pyros, or Hydataos. Finishing the Southern Front hasn't really made me feel accomplished as any zone in Eureka did.
While my own opinion is somewhat negative on post-Bozja, I still do believe that Bozja itself is a great new addition to FFXIV and I hope that they continue to build off of what they have started within Bozja.