Depending on the version of Reaper of Souls you have pre-purchased (or purchase in the future) you can expect the following:

• Reaper of Souls: Digital Standard Edition – One (1) Hearthstone Expert Card Pack, delivered to your Battle.net account starting March 20.
• Reaper of Souls: Retail Standard Edition – One (1) Free Hearthstone Expert Card Pack, available in your Reaper of Souls box as a redeemable code.
• Reaper of Souls: Digital Deluxe Edition – Three (3) Hearthstone Expert Card Packs, delivered to your Battle.net account starting March 20.
• Reaper of Souls: Retail Collector's Edition – Three (3) Hearthstone Expert Card Packs, available in your Collector’s Edition box as three separate redeemable codes.

Note: These Expert Card Packs require a Battle.net account to be redeemed, and a maximum of five bonus Expert Card Packs can be redeemed on a single Battle.net account. If you aren't already playing Hearthstone when the bonus Expert Card Pack keys are granted to your Battle.net account, don’t worry—they’ll be waiting for you in-game as soon as you download Hearthstone for FREE and get through the introductory missions.