Pokémon X and Pokémon Y

They could probably pull the same stunt they did with Bite (Normal > Dark) and make Swift become Light. The big problem with adding a new typing this late would be adding enough of them to have variety in proportion to the total number of pokemon without flooding X and Y with them to a point of nuisance.

I suppose, but still.
Could also have some old pokémon evolve into a dual type with light eventually. Or just give older pokémon the light typing out of nowhere, like with magnemite and steel.
Like making ampharos and its evolutionary branch electric/light.