I can definitely see the inevitable Gen 5 remakes follow the same route as Gen 4. One would be a super-faithful remake of the original two games, while the Legends games would expand upon the lore of the story (can easily see a Legends Kyurem or whatever the original dragon was).
As for Generation 9, it would make a lot of sense sales-wise for the mainline games to remain relatively traditional, as there is an audience for it and I think it’s more accessible. However, I don’t think Game Freak would want to experience sustained backlash like SwSh did, and more traditional Gen 9 will inevitably bring that unless it brings over elements from Legends Arceus.
I personally think it would be best if Gen 9 took the successful stuff from LA while still maintaining some traditional elements. Then you can use the Legends series to continue experimenting with ideas that can rally shake up and evolve the Pokémon formula.
TLDR:
- Remakes are traditional and almost 100% faithful to the original game, just more modern-looking
- Legends games expand upon the lore of the generation and are more Monster Hunter like or open-world, and is essentially the l breeding ground for new ideas
- Newer Generation games are a careful mix of the two above styles, taking what works from each while adding it’s own ideas or gimmicks
- Let’s Go remains the same, really