The consensus in the broadcast business is that HDR is a real improvement, 4k is great for monitors (where you are sitting close and the pixel scale works with the circles of confusion), but mostly a waste on a telly unless completely unreasonably sized.
HDR, especially HDR that actually means it, lots of things sold as HDR do not manage the required brightness or required graduation in the black end of the scale, is a very clear improvement, 4k less so for telly.
HDR also has the virtue that it can reasonably be compressed into a SDR image, so one camera and production chain can do both with some fiddling, the chain does not even need to be 4k capable, bog standard 3G-SDI will get her done, as 4k is basically a different gamma curve so new monitors and a new grading monitor, but all the switchers and routers can stay more or less unchanged.
Regards, Dan.