Kyurem is no new pokemon, its been in Black/White from the start as the third main legendary pokemon. Keldeo though is an event pokemon. In fact they have 2 others they have yet to unveil, Meloetta and Genesect.
Also why do people think they are going to release pokemon Grey for the DS? Releasing a pokemon game for the 3DS would be a priority for Nintendo at this point, because you KNOW that pokemon is a game that sells hardware. Also think about it carefully, normally Nintendo releases a third iteration of the 2 main generation games a year after they come out. In this case Nintendo didn't have any releases last year which means they are taking 2 years to develop the game. Why would an enhanced version of a game that already exists take them 2 years? The only explanation is because they are working with new hardware and are trying their best to utilise the full capabilities of the new hardware.

















