There is one aspect were 4K can make a difference. And that is watching still images. Fine detail is not as easy to spot at 24 fps but watching a still image and you can see a difference. Its also more likely that you move closer to the screen when examine a still image then you do watching a movie.
TVs aren't just for video anymore. They can browse the web and display your 8, 12, 15 and 18 MP images at a higher resolution than any laptop or tablet. Sure, it still won't be full rez, but it's getting closer.
Imagine being able to surf the web from your couch and actually read the page from across the room. Imagine actually seeing at least some of that resolution your SLR produces.
These are multimedia monitors, not TVs.