I'm going to teach you to be just like serebii, pokebeach, pokejungle, and vera.

Go to Google images and sort by last 24 hours or twitter and search for
ポケモン (pokemon)
コロコロ (corocoro)
コロコロフラゲ (corocoro furage)

If anything happens, it will come up under those search terms. Also check the BW general on 2ch's news4vip board and of course the pokemon board. You will know we have a leak when multiple people with japanese accounts post the same cover.

ミュウツー (Mewtwo) may be relevant this time around