^IMO, we should be watching out for the scans this week, between December 10-15. The scans of the magazine usually get leaked before the magazine's actual publication date. I've had experience with CoroCoro with Pokemon Diamond/Pearl.
To be honest, CoroCoro actually DID NOT reveal all 493 pokemon through leaks. They might've revealed...hmm...maybe 15 new pokemon during the game's production that we had no previous knowledge of. Shieldon, Cranidos, Carnivine, Burmy, Turtwig, Piplup, Chimchar, Cherrim, Buneary, Electivire, Roserade, Palkia, and Dialga are the ones I can remember off the top of my head that CoroCoro did reveal.