How good is the game engine of FFXIV?

[TheVigilant]

I'm curious how good is the engine FFXIV is currently running on and how much innovation and upgrade can be done to it and how it would do in the long run?
Seeing as how WoW's engine successfully managed all the improvements being added to the game for more than a decade, I'm hoping the FFXIV dev team chose an engine that will keep FFXIV aging well and still competent in the long run gameplay-wise, graphics-wise and so on.