Update: The official Japanese Pokémon TCG sites have updated with even more card information and details in conjuction with the official release of the September 2011 issue of CoroCoro. The additional details are listed below.
The booster boxes for this set (seen below) reveal that Minccino and Luxray will be in Psycho Drive, and Elgyem and Bisharp will be in Hail Blizzard.
Double Colorless Energy (seen to the right) will be an Uncommon card numbered 052/052 included in Hail Blizzard
A teaser image of Ralts from Hail Blizzard (seen below) was released, and the official blog explicitly stated that one of its evolutions, Gallade or Gardevoir, will be an EX card.
The numbers of the promotional cards listed below were revealed: Battle City (102/BW-P), Luxio (103/BW-P), Riolu (104/BW-P), Meowth (105/BW-P), and Lucario (106/BW-P), leaving another 11 card gap in the BW-P Promotional cards for the September Gym Challenge promotional card pack.
Sunyshore.com and Collectorviper.com have released a high quality scan of the CoroCoro pages featuring the set, and high quality images of the cards can be seen below.
BW3 Booster Boxes
In addition to Mewtwo-EX, the September issue of CoroCoro has also shown images of additional Pokémon. These Pokémon are Pikachu, Grimer, Meowth, Riolu, Lucario, Luxio and Vanillite. Meowth and Grimer are from Psycho Drive, and Pikachu and Vanillite are from Hail Blizzard. In addition, Meowth, Riolu, Lucario, and Luxio are promotional cards alongside the two sub sets. Translations of the cards can be read below.
Psycho Drive and Hail Blizzard will be released on Sept. 16.
Psycho Drive cards
Hit Points: 70
Double Scratch ダブルひっかき
Flip 2 coins. This attack does 10 damage times the number of heads.
Cat Kick ねこキック
Hit Points: 70
Nasty Goo ベトベト
Flip a coin. If heads, the Defending Pokémon is now Paralyzed.