I wouldn't necessarily want Gen 8 to look like Torna in terms of texture depth. I think Town would be a good style to use for Gen 8. For Yokai Watch 4...I mean it's Level 5, Their first title blew other Japanese giants out of the water when it comes to stylized visuals. That's a high bar for Gamefreak, but it's doable. Town already looks pretty close to Yokai Watch 4 so I think Gamefreak will pull it out for Gen 8 and continue to get better. Nintendo's first HD game was NSMBU and now look at them. It takes time to grow these artists skill sets.
Especially since Gamefreak has been working on crap hardware for decades. Don't kill me, I love the GB-DS lines to death, but let's be honest here, the handhelds did not give them the push they needed because every iteration did only just enough.
And let's not forget that Sony and Microsoft (in fact, most publishers) had their initial struggles with HD development as well.