Everything has an end. Someday FFXIV will be replaced by something as well. It won't be anytime soon. But it will happen someday.
As long as people have emotions, this game is going to thrive. Just because of the story. Emotions causes attachment. And attachment causes people to stick to the game. (Also is the reason why it is hard to criticize the game due to the backlash of this)
Even ultimates are easy. I don't feel any difficulty in the game at all anymore. I can see everything getting dumped down by this trend in raid difficulty. I hope someday we can have something higher than ultimates in difficulty and atleast make week 1 dps checks relevant for once, but probably won't see that.