At the end of a new Black 2 and White 2 commercial in Japan, a title card presents a pending announcement to the Pokemon fandom. The title card announced, “We at Pokemon want to share the latest news with you. Scheduled announcement: January 8th.â€ť
Junichi Masuda tweeted that he had finished filming a Pokemon Smash! episode. Masuda typically comes on Pokemon Smash! for announcing new games. As Pokemon Mystery Dungeon: Gates to Infinity has already been released in Japan, it will most likely be a new game. Speculations allege the announcement to present Generation VI, with the evidence being the anime has already completed its run through Unova.
There is no definite answer as to what will be revealed, so we will all hear the big announcement January 8th.
(Special thanks to Charmander009 for pointing this out)