As more and more people purchase 4K TVs, more and more people will demand 4K broadcasts. We are seeing that here right now. I got into HDTV in 1999. There was little HD programming available at that time and it took many years but look at where that is today.And will many OTA broadcasters actually send out a 4K signal? I don't think that they will. It will make more economic sense to offer multiple HD channels (with HDR) using the same bandwidth as a single 4K channel.
How ATSC 3 Changes Broadcasting for the Better (It's Not Just 4K) - Studio Daily