At BlizzCon today, Blizzard revealed to fans that if you are a devoted WoW player, you can get the upcoming title Diablo III for free.

Players who sign up for the World of Warcraft Annual Pass, will get the ability to download and play the digital version of Diablo III for free.  Once the term of your Annual Pass is complete, you can keep the download.
Annual Pass subscribers will also get an exclusive WoW mount called the Tyrael's Charger and will be guaranteed access to the next WoW Expansion Beta.

The World of Warcraft Annual Pass is a 12-month WoW subscription that can be paid in monthly installments.  Blizzard also stated that you must be 18 or older to gain access to the Annual pass.

Click here to learn more details on the Annual Pass.