[Xyphlan]

The idea of new types is certainly intriguing, and could have a profound impact on the usability of some Pokemon. Unfortunately, I just don't think it's likely. Introducing new types, when they already have so many pokemon, would result in a notable shortage of those types, when compared to pre-existing types. While some Pokemon that already exist could fit as light or sound, (Exploud comes to mind)they would still be quite rare.

I can't really think of how sound or light would interact with other types. Light would probably be super effective against dark and ghost, but I don't know what would be good against it. I can't really think of anything that sound would be good or bad against. Though one thing can be said for sure: If new types are made, they will be bad against steel. Because everything is.

Steel and Dark were mostly introduced in 2nd gen because Psychic was ridiculously overpowered as a type. The only types good against it were bug and ghost, which sucked for plentiful reasons. Dragon is arguably overpowered, but I'm not sure it's enough to warrant a new type.

But I'd be lying if I said that I wasn't excited for new types.