The boxart is clearly a mock-up - the PS4 version carries an image of the Xbox 360's hard drive - though Amazon is a fairly credible source. It could be a placeholder, put up in advance of an official announcement. It could also be a fake, thrown together by some malicious intern for shizzles and gizzles.
Rockstar and parent company Take Two have repeatedly denied rumours about the existence of a next generation version of the game, with studio co-founder Dan Houser objecting that "there's plenty of power left" in Xbox 360 and PS3. Rockstar North does appear to be working on a game engine for "next-gen platforms", however, and Take-Two has an "extensive pipeline of unannounced titles" in the works for the new consoles.
Update: Amazon.de has now removed the pages in question. There's still no word from Rockstar.