If they wanted to take an expansion to rebuild all of this and get everything up to speed, making the game "future proof" for later expansions and all of their database needs, as well as refactoring the netcode to be more responsive and workable, I wouldn't begrudge them one bit for doing so.
Now, before the "SE Defense Force" chimes in with "YOU CAN WORK AROUND THESE ISSUES!!", please
stop missing the point entirely.
There's no reason WoW should have better database servers than XIV, and when you say "You can work around it", you're acknowledging that there is indeed a problem to work around in the first place, one that modern AAA MMOs don't have and one that XIV certainly shouldn't have either.
So I'd say take the time to fix the issues you need to fix, devs, even if it means rebuilding most of the game. The game is more than prosperous enough to do so at this point and, after all, any "fixes" implemented without doing a full revamp are just going to be bandaids in the long run.
XIV is a wonderful game and absolutely worth putting this kind of love and care into.
PS. This is not going to be an OPTIONAL change for the game, FYI. If they're struggling this hard to make due with their current database servers, they're eventually going to find themselves up against a wall where they either cannot add new expansions or need to start deleting expansions from the game to make room for new ones.
PPS. They've also made a change like this once already, back before the game was profitable, where they were building 2.0 while keeping 1.0 running AND were adding content to it.
You can learn all about it in this awesome documentary:
https://www.youtube.com/watch?v=Xs0yQKI7Yw4