I think that the only thing that's really needed is different type combinations, not new types. There is one thing that confuses me about the whole darkness and fighting thing. What about scrafty? It's dark AND fighting, so it's contradicting the fighting is honorable while dark is not [...] Can anyone explain the dark/fighting combo to me? seriously -.-
It probably won't happen. Like, ever. But it would actually be very nice if it did. It could balance out some of the less balanced types like Poison. And maybe it also could be something else that Steel takes normal or better damage from. And though Light type is a terrible idea since depending on one's definition of Light it would either be a clone of Psychic or Electric, there still are possibilities. Sound could work, or maybe Cosmic, or in theory Nuclear even.
As for the Scraggy line, I guess flavorfully the looks fit with the Dark-type, and its behavior fits with the Fighting-type? I really don't know.