What annoyed me the most is that the title Black and White just screams "Light type." But Game Freak didn't announce it. Black and White is a misleading title IMO.
I still consider it a theory even though I do agree that there won't be Light type. If there is gonna be one, I can imagine it being super effective against Ghost and Dark types which completely eliminates "no weakness," but doesn't deal as much damage as Fire, and Dragon type. It can resist Psychic, Fighting, and Bug types, and become immune to Ghost types, but is weak to Dark type moves.
Other than that, Game Freak shouldn't have bothered naming 5th Generation main stream games "Black and White" in a first place. That's my main gripe about the decision making in 5th Generation.