For PC, the chance is currently 100% for a UI change, since they've already started on it. Graphical overhaul? I'd say roughly 10% chance if FFXIV is any more of a miserable failure; I'd then expect some kind of migration of FFXI on to the Crystal Tools engine and perhaps some temporary use of FFXIV assets.
But XIV shows that SE still can't produce a usable more modern gfx system. XIV's graphics at times are pretty cool, some of the character rendition is good, but it has a horribly close draw distance which means as you walk there's a visible stark line between low and high res. textures which 'rolls' as you move along. It's as ugly as sin. Some areas are great, I love Gridania, but this ugly low/high transition really detracts.
And let's not talk about the horrible performance it has, needing bleeding-edge gfx cards to be able to turn up the settings .. and it STILL uses the same rendering system that means hardware-based AA has zero effect and even at full there's a noticable shimmer with features such as trees as they sway.
No, I'd prefer to keep XI's dated but entirely usable system rather than XIV's which looks cool in static pictures but is dire to move around in.