The 12-14 styling appealed to me even more because of the change in 2015, not despite it. I prefer the more raw look of the earlier style grille to the more polished look of the later one, though my taste in car styling has always been outside the mainstream (Saab 93 & 96, Porsche 356 coupes and convertibles, 914, etc.). As good as the Fusion looks, I like having something that looks different, not "me, too." That could change, though, when I see the '15 in person. You can only tell so much from photos.
In the back, the '15 also has a horizontal crease between the bottom of the tail lights and the top of the bumper that is common on Honda Civics, several Kias, and other Ford models. Again, I like the way the '12-'14 looks different rather than similar. The slimmer tail lights on the '15 are also less distinctive.
The main reason I'm glad I got a '14 is that the '15 can not be bought with a manual transmission and the SE sport package (cloth seats). As in '13, if you want the fog lights, 4-wheel disc brakes, and trunk spoiler (sedan), you have to order the more expensive appearance package (leather seats) to get it with a manual. Sounds dumb to me.
The main reason I might prefer a '15 would be for the interior changes. The 17" black/machined wheels with the SE sport & appearance packages also look nice, but I could always put a set of them on my '14 later.
If anything were to happen to my '14 that I had to replace it I would miss it, but I could still be happy with a '15. The convenience of a hatch would probably also win me over, despite my preference for the proportions and styling of the sedan. (I underestimated how often I would be putting stuff in and out of my trunk and how much less convenient it was than with the hatches I've owned for so many years. Not having a rear wiper has also been more annoying than I expected.) Function over form.