>>33309339I'd say the type chart is set for a few more generations. There's still a lot of unexplored combinations. They'll add new types when it gets stale or the chart starts to become somewhat imbalanced again.
I will say that, in terms of Cosmic and Light, those are sort of already covered by Psychic and Fairy respectively. Maybe Normal as well. Functionally, Cosmic is just "space faring" and, especially after Gen VI introduced Fairies, Psychic types and their trainers took a hardline into being the "metaphysical" or "spacey" type. Fairy assumed the role of being the "magical" type, which also covers Light by virtue of them being the more "angelic" type of the whole lot. Normal picks up any leftovers as it includes Pokemon like Chansey and Arceus still, who could easily fill in the role of being "virtuous" as Normal, in some sense, is the "unaligned" type -- which I can imagine a being of Light would most likely fall into as well.
On the flip, Dark-types are dirty fighters, scoundrels, creatures of the night, etc. That's not exactly the "opposite of Light." When people talk about a Light type, they really mean something "heavenly" -- not actual physical light. The types that oppose Dark, for now, seem to already fill that role or something else anyway. Fighting is "heroic" and can take on badguys; Bugs kind of are "heroes" too (if you take their association with tokusatsu into consideration); and Fairies, as I said, fill in the "magical creature of light" role.
Psychic is weak to Dark because Dark clouds their judgement, it blinds them, it blocks out the cosmos, etc. The only weird bit with Dark types is Ghost because fuck if I know why they're weak to Dark-types.
Fairies throw in the mythology of Fairies as well with their weaknesses/strengths, so they're not purely a Light type. And neither is Psychic purely a Cosmic type. But, again, my point is that those two types are already "covered." There's no reason to include them unless they get desperate.
