The official Pokémon website has announced the next Pokémon TCG expansion, HeartGold SoulSilver — Unleashed. Below is some of the information from their press release.
Raikou... Entei... Suicune... Alone, each of these Legendary Pokémon is a force to be reckoned with, but let loose in pairs, they become amazing LEGEND cards! In the Pokémon TCG: HS—Unleashed expansion, you'll find Pokémon Prime bursting at the seams, powerful Pokémon like Jirachi and Shaymin raring to join the battle, and Pokémon LEGENDs joining forces for twice the excitement! Are you a powerful enough Trainer to command what's been Unleashed?
With more than 90 cards, the brand-new Pokémon TCG: HS—Unleashed expansion will arrive in stores nationwide on
May 12, 2010.
Features of the new Pokémon TCG: HS—Unleashed expansion:
* Legendary Pokémon—Entei, Raikou, and Suicune—appear in pairs on Pokémon LEGEND cards
* Discover six amazing Pokémon Prime cards, including Tyranitar and Steelix!
* Introduction of Chaos Control and Steel Sentinel theme decks
Source:
http://www.pokemon.com/us/news/tcg_hgss2_announce-2010-03-15/