Sony's PlayStation 4 technically already supports 4K video playback, so what if the new fancy PS4K or PS4.5 is just a default PS4 with a 4K Blu-ray player thrown in?
Back in 2013 before the PS4 released, Sony exec Shuhei Yoshida confirmed that the console would indeed support 4K video playback and pictures on launch. "The official answer is that the PS4 supports 4K output but for personal contents, like photos or videos. Not games. PS4 games do not work on 4K." This means the PS4 can already technically play 4K Blu-rays, but the console still has limitations.
The current PlayStation 4 model might support 4K video playback, but it doesn't have a 4K Blu-ray player installed. Plus, it only has HDMI 1.4, which limits 3840 × 2160 at just 24 FPS. The PlayStation 4 was released before Sony had established the UHD Blu-ray spec, so that's one of the reasons the console didn't ship with a 4K player installed.