It could be leaked anytime from now on.

We are waiting for a whole book about Pokemon and not just a few pages from the magazine. This is the last edition prior to the games being launched worldwide.
http://www.corocoro.tv/pokemon_book/

Must check every once in a while:
https://twitter.com/search?q=corocoro&src=typd&f=realtime
https://twitter.com/search?q=corocoro%20pic.twitter.com&src=typd&f=realtime
https://twitter.com/search?q=コロコロ&src=typd&f=realtime
https://twitter.com/search?q=コロコロ pic.twitter.com&src=typd&f=realtime
http://kohada.2ch.net/poke/
http://awabi.2ch.net/gamenews/
http://hayabusa.2ch.net/news4vip/
http://jun.2chan.net/31/futaba.htm
https://twitter.com/pokejungle
http://serebii.net/index2.shtml

Use also:
ポケモン (Pokémon)
コロコロ (CoroCoro)
コロコロフラゲ (CoroCoro leak)
With Yahoo and Google web and image search. Set it to show recent results only.