Here's the full statement from Zynga.

"Greetings PetVille players,

Thank you for supporting PetVille and for being a loyal player! We're sorry to inform you that PetVille will be shutting down on Dec 30, 2012. In place of PetVille, we encourage you to play other Zynga games like Castleville, Chefville, Farmville 2, Mafia Wars and Yoville.

We appreciate your participation in PetVille as it helped make the game a fun place to meet and war with friends. As a loyal PetVille player, you are eligible for a one-time, complimentary bonus package in one of either Castleville, or Chefville, or Farmville 2, or Mafia Wars or Yoville. You can start the process by logging into PetVilleand clicking on the "Redeem" button. Please note that this offer will be valid only until Dec 30, 2012.

Thank you for your time in PetVille. We look forward to seeing you again in other Zynga games."