I asked the same question at a local Gamestop. They laughed at the thought of a midnight release for a Pokémon game, saying that there's no way that kids' parents would take them to Gamestop at midnight to buy it O_o. They said they were opening at 9, though, and are not doing any special preorder bonuses. According to
this article on PokéBeach, they're offering the Prima strategy guide for 20% off to people who purchase one of the games, but that's it (the article also lists bonuses that other stores are offering, if you're interested).