I've been saying since basically X that they should use a graphic style that is actually capable of fully capture the character designs in the game.
Especially with Nomura's art: I love his art (the designs, on the other hand, are a mixed bag), although I dislike his current, very sharp and KH-looking style used in games such as Dissidia (mid and late 90's Nomura still the best). Thing with him is that his characters tend to look way too pristine and silicone-like in-game, as well as having clothes and hairstyles that might look alright in a drawing, but when you have to see that in 3D and with a more realistic approach...
Take a look at Tidus: as a design, despite the stupidity of his outfit, he doesn't look half-bad:
And then you see his Meg Ryan face. And how round and lacking in detail everything is. I mean, it's not atrocious, but there surely are much, much better styles for him and the rest of the characters for that matter.
FF XII was so great in that department, what with the stylised graphic look they went for (the kind of hardware limitations they had to endure probably helped here): Yoshida's designs were important, too. FF XIII is another like X imo, while XV is much, much better in that regard but you still get very awkward and stupid-looking characters such as younger Noctis (he looks good in concept art and in the anime, but not in-game (to me, at least). All it took to fix him there was non-embarrasing clothes and a normal enough hairstyle, Nomura!).
So yeah, although I'd rather a different, more unique style (like XII), cell-shading wouldn't be automatically bad and could be even good considering how poorly these concepts
can translate into the game: remember that "cell-shading" is not just one unified look, but rather an approach. It cool look similar enough to DQ VIII, Ni No Kuni... or something completely different and, say, more complex and realistic.
I think that the next game is going to look kinda like Agni's in terms of character modelling style (so, pretty much like XV). How it's going to look depends on the artistic style of the characters and world themselves.