Speaking primarily about adopting aspects only.
The fighting style of Final Fantasy XIII-2 is roughly the same as it’s predecessor, and it included reaction commands that have been featured before like in Kingdom Hearts 2. The battles weren’t hard but I’m sure that also has to do with the need to speed people through the demo. So it wasn’t very exciting strategically, however, cinematically it was very enjoyable.
Seeing the fighting style in action, I saw how easily it could be for future Kingdom Hearts titles to take from it. I don’t think Kingdom Hearts should ever be a turn based RPG, they’re not nearly as much fun to play. However, the camera views, wide lens, and flow of animation when the characters fight, especially during the reaction commands, made clear the potential of effects that KH3 could potentially utilize.
I like the bright and colorful style of Kingdom Hearts, but I think what many fans enjoy, is those hints of artistic CG animation that the opening and ending clips contained in the PS2 titles. To make a title that took on that style of animation would be instantly appreciated by fans, who are tired after waiting forever for the final installments of the story and are growing tired of the multiplatformed handheld games.
The greatest challenge they would have in animating the game in the semirealistic style is to make it work with the Disney characters whose cartoon attributes have been the primary influence on the design of KH characters. However, this would also open a window for Disney Pixar worlds to be explored and they wouldn’t have to be jeopardized by style conflicts. There is also potential to bring back the Pirates of the Caribbean world or incorporate other live action titles.
They’re rough ideas and if they continue to pursue the style that has already worked, I wouldn’t be upset. But when I play FFXIII, I feel like if you removed the menu and other screen additions so you could only see the animation, it would be just like watching a movie. In the FFXIII Versus Trailer at TGS 2010 the fighting animations were sans screen menus and it looked like Advent Children.
If they keep the recognizable Kingdom Hearts style I hope they focus instead on continuing to make the action aspects enjoyable. Birth by Sleep had a lot of innovative additions to the battle system, these are the strong points that I think are the most important to focus on. If they could add multiplayer functions again, even more fun.
I’m getting way off topic, but the gist of this is, the Kingdom Hearts worlds generally appear bigger than they feel when you play through them, expanding the maps and making them more interactive combined with the creative battle views and reaction commands will make the future of Kingdom Hearts great and remind all the players who didn’t jump onto the handheld titles why they liked the series so much to begin with.