I think GameFreak has tried to shy away from the "realistic" art style, as it seemed they had no idea what the various textures on the Pokémon looked like. For example, are Charizard leathery or covered in scales? Bulbasaur's skin, is it slimy like a poison dart frog, or rough like a plant stem? Do Jigglypuff have fur, or is their skin smooth like human skin? Too many design decisions, and having 800 + models to texture would require quite a lot of storage space too.The team who's working on Pokken's models need to work on the models for Gen VII as well...
The result was, for some time, that Pokémon were created with as little texture detail as possible. Just look at the Pokémon models in SSBB, they all look like plastic toys, unnecessarily so compared to all the other trophies. Not too bad by themselves, but it creates a terrible dissonance with "realistic"-textured environments. Poképark Wii is another horrible offender. However, it seems like cel-shading is the future, at least for the main series games. That keeps the Pokémon low-detail and colourful, but still matching the art style of the environment. This match of environment and creature design is to me the main reason why XY and ORAS are the prettiest games in the Pokémon series.
For a spin-off game featuring fewer Pokémon, however, it might be feasible to try some high-res textures like they seem to do here. Time will tell if the experiment is repeated again some time in the future.