IMHO:
I think they will stay the course for multiple reasons.
Yoshida appears to prefer to keep a smaller more efficient team. A radical overhaul of the game would need a serious recruitment spree and neither Yoshida nor SE's bean counters have shown that that's something they want to pursue.
The game is successful therefore the recipe is working... right? It's pretty easy for a developer to fall into the trap of being almost arrogant about their own game, doubly so when it's big of a success story on all accounts as FFXIV has turned into over the years. Yoshida has shown signs of this over the years right from ARR's launch with the Warrior debacle.
Will things ever change? The way I see it it'll take either WoW having an ARR style rebirth of its own or some other competitor coming out of the blue to steal the momentum away from FFXIV. That'll trigger the inevitable next gen MMO from SE with FFXIV getting handed over to a fresh young team in the same way FFXI was. What we'll get out of that is anyone's guess but I'd expect some shake ups to drag more life out of the old game.