Red & Blue - Colours of Charizard and Blastoise. Main legendary is Mewtwo (neither of those colours nor of a related type), enemy group is Team Rocket.
Gold & Silver - Main legendaries are Ho-Oh and Lugia (which are vaguely those colours), enemy group is Team Rocket. Plot is reviving Team Rocket.
Ruby & Sapphire - Main legendaries are Groudon and Kyogre (which are vaguely those colours), enemy groups are Aqua and Magma. Plot is worldwide drought/flood.
Diamond & Pearl - Main legendaries are Dialga and Palkia (which have gems that look like these stones), enemy group is Team Galactic. Plot is the destruction and recreation of the universe.
I think it can be assumed that the names Black and White have almost nothing to do with anything, except probably the colour scheme of the main legendaries. So no, don't go expecting Team Daytime/Nighttime, a new Light type, yin-yang themes, life/death, good/evil, joining Team Rocket in Black version, or anything like that. You should expect a "good vs. evil" theme, though, but all the games have that.
Remember how everyone was hoping for a Light type, a Psychic/Fighting/Dark starter triangle, Fire/Bug Pokémon, etc. etc. etc. in the 4th Gen? Remember how all that didn't happen? Just think about it...