As I understand it, the PS3 already meets the specs for 4k as is (though, please correct me if I'm wrong). There's just no market. Without content, displays, or audience, there's simply no reason.
Originally Posted by darklordjames
"Maybe PS4 will do the same thing for 4K BD, as PS3 did for BD."
Modern Bluray is the last mass-market, disc-based video format. Calling it "mass market" is even pushing the term a bit, as it will never do as well as DVD did. People have already proven that they are pretty done with discs. Anything that comes out later will have a lot in common with Laserdisc, an extremely niche product that is vastly overpriced.
As with all things format related, never say "never." While it might seem like physical media is on the way out right now, there's nothing preventing it from returning in the future in some other way that we can't yet imagine.
Back in the '50s, technophiles were declaring the end of film and the movies (because of TV, home cameras, the then-new technology of video, etc). It didn't happen. The film industry hurt for a while, but then bounced back stronger than ever in the '80s--in the midst of the home video revolution.
A future physical media may or may not be disc based, and it may or may not ever exist. Nothing is certain.