It looks sorta like a Tyranitar to me, to be honest. I'm probably wrong but I think it's either that or one of the Kyurem forms, or Groudon. I'm aware that's three completely different Pokemon, but that's all I got xD
I'm hugely excited about the expanded Pokedex. The Black/White regional dex was big enough, but to add 144 other Pokemon is just awesome. I'm already pleased with all the Pokemon that have been revealed so far:
(Low quality image, sorry).
I see Arcanine, Lapras, Tyranitar, Weavile, Mareep, Lucario and Metagross. And I love all of those Pokemon, so yes, I'm very, very pleased with the expanded Pokedex so far :D