With Generation 10 on the horizon for Pokémon, there comes another opportunity for the rare occurrence of brand-new types to be added to the iconic franchise. While new Pokémon are pretty much a given, many are hoping that perhaps a new type may also be making its debut in Gen 10. With the last type addition being Fairy, several generations back, it is certainly time for something new. However, with so many types already, it's hard to imagine where the Pokémon franchise could intend to go from here.
As there are tons of Pokémon fit into types that just don't feel right for them, such as many of the Pokémon grouped into the Normal type, there are plenty of ideas for Pokémon to choose from. Simply looking at currently existing Pokémon as well as some of the moves that many Pokémon frequent can open up doors for tons of new types. Additionally, many types, like Dark, don't necessarily have something that feels like it's opposite, and therefore even something of that nature could be potential for a new type of Pokémon.
5 Fossil
Something that will be familiar in Pokémon are Fossil Pokémon, but that is not because it's a type. In fact, despite that Fossil Pokémon are considered a specific group of Pokémon, they generally all are part Rock-type which simply feels boring for some of these interesting and prehistoric beasts. Since Pokémon has already decided to group these Pokémon and give them a name, there is no reason that they couldn't be turned into their own type.
Many players have suggested a Dinosaur-type to mirror the much beloved Dragon-type, but Fossil-types could include these Pokémon as Fossil is just a more generalized approach to the same idea. As for their type matchups, this typing could be similar to rock in terms of strengths but then vary slightly in its weaknesses to create some more variety. Then each Fossil Pokémon could have a subtype that would essentially act as their primary defining type while Fossil served as their secondary.
4 Cyber
Cyber-type Pokémon are another type that could encompass some already pre-existing Pokémon as they could include both futuristic Pokémon like Porygon, who is quite popular due to the banned Porygon anime episode, but also some newer Pokémon from Gen 9, such as the futuristic variants featured in Pokémon Violet. With so many new Pokémon that feel as if they are computer-based, Cyber is a great option for a new type and could introduce some very interesting new designs that aren't just Paradox Pokémon. However, those Paradox Pokémon do prove that concepts for this type of Pokémon are already there and could be expounded upon.
Given that these Pokémon would be technology based in nature, it seems only fitting that they have some relation to Electric-types in some way. This could either come in the form of a weakness to Electric as if the attacks from that type would essentially fry the system of the Cyber Pokémon. However, it could also work in the opposite sense where electricity kind of powers up the Cyber Pokémon, so instead of being weak to it, they are actually resistant to it. Water-types could work in a similar sense in that they work to Electric-types as well.
3 Light
With the existence of Dark-type Pokémon, it only stands to reason that players should have Light-type Pokémon as well. While some may argue that Fairy-types could be considered a counter to Dark-type, they're not a true match. While this type would likely involve mainly designing new Pokémon, as there aren't many that already fit the bill, the ones that do, however, are pretty significant. For example, Arceus would be a great option to be converted over to Light-type, were it an option.
As this would be close to Fairy and the opposite of Dark, when forming type matchups, Pokémon would need to consider how these specific type pairings would play out and then go from there, as this type could accidentally end up very over- or underpowered if those types are not taken into account. For Light-types, many of the new Pokémon designs can be focused on using brighter colors as well as perhaps featuring unique effects that play with the light. Something of a similar vein could also be utilized as a move.
2 Cosmic
Cosmic-type is a highly sought-after type by many players, given there is a lot to work with in terms of design, especially with all the various constellations that could be used to inspire specific Pokémon. More specifically, many players are eager to see more cosmic zodiac-based Pokémon designs which could be very interesting.
Although the pool of current Pokémon that could be applied to this Pokémon type is limited, that is not necessarily a bad thing, as it allows for the introduction of new Pokémon and not just a new type announcement that primarily consists of a bunch of Pokémon nobody ever bothers with. However, there are some Pokémon that could be applied to this type such as Clefairy or Clefable, who are said to store moonlight in their wings, which definitely strikes as being more of a Cosmic-type.
1 Sound
Sound is perhaps the type that would genuinely make the most sense for a new Pokémon type, as there are plenty of Pokémon entirely based around sound and moves that are essentially just Pokémon shouting at each other. With Pokémon like Loudred, it's odd that Sound is not already a type that exists, as it is even described as the loud Pokémon. Given that sound has some interesting effects on its environment, this could have very interesting type matchups as well.
For example, sound travels faster in water, so it stands to reason that they would perhaps have an advantage over Water-type Pokémon, potentially even stunning them with the effect. Similarly, they could have an advantage over Psychic-type Pokémon as well, since Sound would be very disruptive, causing a loss of focus. At the very least, Sound should be resistant to Psychic in Pokémon even if they have no advantage. While there is nothing that feels like it would obviously have advantage over Sound, there are some things that could make logical sense, such as Ground or Flying, which could potentially have more effects on Sound than it would on them in return.