GTA V could very well launch this October, on time for the holiday shopping season, according to Rockstar North character animator Alex O'Dwyer, who mentions the title and launch window on his CV and LinkedIn - this has since been pulled, as noted by Joystiq.
Max Payne 3 is slated to ship next month, and it would be a bit odd for Rockstar to ship two huge titles in the same year. On top of that, publisher Take-Two Interactive is planning on launching BioShock Infinite this October as well, so the company may not want to risk any chance of GTA cannibalizing the new Ken Levine title.
It was only last month that Sterne Agee analyst Arvind Bhatia said that a 2013 launch for GTA V now seemed likely based on retail channel checks. If GTA V ships in the fourth fiscal quarter for Take-Two (ending in March 2013), the company's fiscal year would still reap a big benefit from the blockbuster release.