There isn't any broadcast 4k content in the US and I'm not aware of any 4K cable yet. What there is are 4K and 4K w/HDR Blu-Rays, a little bit (and growing) of original Netflix 4K and 4K w/HDR content, and I'm under the impression that Amazon Prime has some 4K original content with more on the way. The problem is that not every media player supports 4K much less 4K w/HDR. At normal TV sizes and viewing distances 4K is a bit of an improvement over 1080P but not a huge one. It's when you are close to a display oe with a huge display where you see it the most. On the other hand
High Dynamic Range (HDR) is, in my opinion, a big improvement in the picture - as long as the performance of your next TV is up to the task.
Would I replace a perfectly good 65" 1080P just to have a 65" 4K TV? Nope. But if you are replacing a dying TV, upgrading the size of your TV, recycling the old set into another room, or just have a hankering for a new TV then 4K w/HDR is the way to go.