Some new Corocoro scans hit the net yesterday and they reveal quite a bit of details about the games Pokemon Black 2 and Pokemon White 2. One thing that we know for sure now is that the games are direct sequels to Pokemon Black and Pokemon White. The story takes place 2 years after the original story of Black and White. There are 2 new trainers to choose from and the rival is also different.
Half of the Unova map has been covered with ice for some unknown reason (I'm sure we'll find out though). The new Unova region has new towns, buildings and subway lines to completely new areas.
There's quite a few details listed, so if you want to check all of them you can read the article at Pokebeach.com. I'll post the scans here so you can take a look!