Wow! These Pokémon resemble, or rather, remind me of the angles from Neo Genesis Evangelion. Anyway, what interested me were their names, which is of darkness and light. It's not just their names that pike me interest, but the DSi function as well. I mean, the DSi has a camera! I'm pretty sure that this Pokémon game will be abe to detect actual light or how dark it is the area the player is in.
How will this influence game play? Well, it will make certain Pokémon like Umbreon or Espeon evolve more convenient. Also, other Pokémon could evolve under these different circumstances. There could be moves that require an amount of darkness or light for some Pokémon.
Berries could be effected by the amount of sunlight you actually roam in, like growing faster.
There are lots of possibilities!