A new Pokemon game is going to be announced early next year in Corocoro magazine. No information as to what sort of game it will be, whether it'll be a spin-off or a Pokemon Grey announcement, so curb your excitement. This is coming after rumours of an announcement at Jump Fiesta this weekend.
The next issue of the magazine will be available on January 14th 2012 and will contain what they describe as a world first shocking announcement; if that isn't building the hype I'm not sure what is. When viewed in tandem with the recent web acquisitions including the series, perhaps we can already hazard a guess to what it will be. Either way, expect to hear more as the magazine goes out to subscribers in the New Year.
Source: Serebii