Buy a Samsung SSD when you have an opportunity to do so... those load times will disappear to almost nothing! I play on a Pro with a 4K TV and an SSD and I'll never go back!
I want to do this with my regular PS4 because I'm running out of space and want to upgrade to a bigger drive and thinking maybe going SSD just for FFXIV. Debating if it really makes THAT much of a difference but it would be nice to have!