It's official: After first rumors in the past few days, Rockstar Games published the following news at their newswire page:

"Today, we're proud to announce that Grand Theft Auto V is expected to launch worldwide spring 2013 for Xbox 360 and PlayStation 3.

Developed by series creator Rockstar North, Grand Theft Auto V takes place in a re-imagined, present-day Southern California in the largest and most thriving game-world we have ever created set in the sprawling city of Los Santos and for miles beyond – from the tops of the mountains to the depths of the ocean.
Starting next week November 5, 2012, Grand Theft Auto V will become available for pre-order everywhere and fans can expect a host of new information to become available in November."

Although there is no information about a PC version of GTA V, we're expecting a release during the summer.