A UHD bluray PS4 would be cool but my faithful and usually correct crystal ball tells me that UHD Bluray will be a niche of a niche of a tiny niche.I'm kind of hoping that UHD gets a little traction and Sony brings out a UHD compatible PS4 revision (need BDXL drive and HDMI 2.0 with latest HDCP) or maybe pushes up the PS5.
But with sales doing well, they may want to milk this generation for awhile.
Or if they're truly making money on each console from the start, maybe they'd be more open to pushing up the next generation. They're still putting out expensive TVs. I believe they announced new UHD models at CES. The UHD Blu Ray spec is near finalization. Sony should have some patents in that.
Now, a PS4 that can play 4k online videos through Netflix or Amazon? Heck yes!