Yes, according to http://bulbanews.bulbagarden.net/wiki/May_issue_of_CoroCoro_magazine_leaked , 300 Pokemon are accesible in the game(including the 156 Pokemon from Unova). The Regional Pokedex has changed as well, with Psyduck, Arcanine, Lapras, Eevee, Mareep, Tyranitar, Metagross, Buneary, Riolu, Lucario, and Weavile all added to it. However, The Pokedex numbers have changed quite a bit. Riolu is #33, Psyduck is #28, and Metagross is #264.