This has been confirmed for a while but I decided to wait until it went live to announce the new Pokémon Black and White WiFi event. For all international games, Reshiram and Zekrom are available as a mystery gift depending on what version you have. Basically, you will be getting the opposite dragon from the game. Black version gets Zekrom and White version gets Reshiram.
Hit the break for additional bonus included in the event.