The substitute is actually very heavily marketed in Japan.I can't see something being marketed this much as being something as small as a substitute or an item.
Also, why still haven't referred it as Pokemon yet?
I think releasing information at World Championships is very possible.Oh, I'm not saying there is more - yet. I'm just saying that it's likely we'll see a worldwide introduction to this... thing soon enough. And that might include more info. GameFreak should know by now that every Pokémon fan with Internet access and knowledge of even one Pokémon fan site will catch the news pretty quickly, so once the cat's out of the bag in Japan, it's out everywhere, so there's no reason to withhold anything from the International scene.
Now, GameFreak doesn't recognize a cat as out of a bag until they've released it themselves, via official channels, but the publication of CoroCoro is one such cat-release. So once it's official in Japan, there's reason to believe it will be official worldwide before long.