It may be a bit too early to be thinking about Pokemon Gen 10, but it has been on some minds ever since Pokemon Scarlet and Violet released. Just as past games hid details for Gen 9, fans have potentially found potential region inspirations for Pokemon Gen 10 within the games. Whether they are accurate remains to be seen, but there is one pattern that hopefully comes to fruition.
However, it should be noted that Game Freak can break from any potential patterns at any point. For example, there was a time when new Eeveelutions were introduced every two gens, but Pokemon Gen 8 more or less broke from this. Umbreon and Espeon joined in Gen 2, Glaceon and Leafeon in Gen 4, Sylveon in Gen 6, but fans got a Gigantamax Eevee in Gen 8. But even acknowledging this possibility, Pokemon Gen 10 will hopefully continue the potential "new type every four gens" approach currently established in the franchise.
Pokemon Gen 2, Pokemon Gen 6, and Pokemon Gen 10
While fans often discuss potential new Pokemon types, it makes sense for Game Freak to ensure this happens rarely. Not only does it mess with the meta and entire roster every time a new type is introduced, but too many types would simply complicate an otherwise simple game. But there is a precedent for the introduction of new types in Pokemon games. The Dark- and Steel-Types were introduced in Pokemon Gen 2, with there not being another type until Pokemon Gen 6's Fairy. That's a split of four gens, and this could potentially suggest Pokemon Gen 10 would introduce a new type.
Of course, that pattern has a very loose basis since only three new types have been introduced since the franchise's inception. There is at least one potential argument that could support this, though. Many fans are dying for a new Eeveelution since one hasn't been properly introduced since Sylveon, and Game Freak may choose to take this classic approach with Gen 10, instead of relying on whatever its gimmick is. Pokemon Gen 2 introduced Umbreon to coincide with the new Dark-type, and Pokemon Gen 6 introduced Sylveon to coincide with the new Fairy-type. Introducing a new type and Eeveelution alongside it in Pokemon Gen 10 would simply be a power play for the new generation.
What a New Pokemon Gen 10 Type Could Look Like
Whether it happens is up in the air, but many fans have discussed what a new type could look like. For example, the fanmade Pokemon Uranium made the "Nuclear-Type" quite popular, but it's unlikely that a core game would adapt anything remotely similar. Something that does seem plausible is a proper Sound-type, something fans have called on for years. There are several moves that are based on sound that could be altered, while existing Pokemon like Whismur and Chatot could adopt the type. Having a proper Sound-Type beyond that would open up several possible Pokemon designs.
Another possible design could be something like a Digital- or Artificial-Type to emphasize the various Pokemon, introduced throughout the franchise, that are made through science like Porygon and Genesect. Sound seems a bit more fitting for the franchise, especially given Pokemon clone Temtem's Digital-Type, but either could work in a similar capacity. Other possibilities could include introducing a proper Shadow-Type (or Light-Type), something like Abnormal that could work similarly, but oddly, in comparison to the Normal-Type, or truly anything.
Pokemon Scarlet and Violet are available now for Nintendo Switch.