Pretty much this. For optimal viewing distances on your average 50-60 inch HDTV there's dick all difference between the two resolutions and you have to sit closer than you should to be able to see it. For 50 inch 1080p TVs you want to be at about 6 feet and for 60 inches you want to be at about 8 feet and you have to be much closer than that to see 4k on those.You shouldn't be sitting close enough to a TV to see the difference between 1080p and 4k.
4k is basically snake oil for TVs. It's good for large (27-30 inch) desktop monitors and 100+ inch projection screens and that's about it.