Blizzard announced today that 132 cards are headed to Hearthstone in an upcoming expansion called The Grand Tournament.
New hero power cards are on the way, including Maiden of the Lake, which makes the cost of your hero's power one mana. The expansion also adds the inspire ability on new cards. It takes effect when the hero's power is used and grants certain abilities, such as a minion gaining attack power.
Players can pre-purchase packs starting next week prior to the launch of the expansion sometime next month. Blizzard will be offering a deal of 50 packs for $50, which usually only nets you 40 packs. Those who pre-purchase 50 packs will get an exclusive cardback. Check out the source link for more information on some of the new cards.