Bananarama
The light is coming
I don't think that there should be any new types, especially if it's just for the sake of having new types. I prefer the 18 types we already have.
Also, like what was said before, the addition of new types is mainly for the purpose of balancing type matchups. Dark and Steel types were introduced to counter the overpowered Psychic types in generation 2, and Fairy types were introduced to counter the overpowered Dragon types in generation 6. I can't really think of any types that are unfairly balanced, as of right now, so a new type wouldn't really be justified.
Also, like what was said before, the addition of new types is mainly for the purpose of balancing type matchups. Dark and Steel types were introduced to counter the overpowered Psychic types in generation 2, and Fairy types were introduced to counter the overpowered Dragon types in generation 6. I can't really think of any types that are unfairly balanced, as of right now, so a new type wouldn't really be justified.