Even if they are planning a next gen version - the very last thing Rockstar want is for it to leak before they have sold the bulk of copies on current gen. With this in mind - do you think they would send out official box art to retialers - especially leaky european online retailers?
Of course it's fake, mockup, etc ... the real thing is that it IS listed as a PS4 game on a known retailers website. The 'art' is the least exciting thing about this. The fact that it's listed is the real news.
im almost positive only palystation 4 exclusive games come in a blue case. i think third party games come in a clear case. its something ive noticed when seeing different pictures of ps4 games online at different retailers.