Amazon Germany has listed Grand Theft Auto V for the PlayStation 4 system as an official, yet unavailable, listing. Check out the listing here. Of course this has to be classified as a non-confirmed rumor of weather the game will actually come to the next-gen system.
[Update] The listing has since been removed. This could mean this was an unintentional leak or simply not real and a mistake on the retailers part.
Website Post was updated.