MacLeech Most content isn’t OTA any more.
Unless the event is broadcast on NBC, ABC, CBS, or Fox, OTA isn’t even a factor.
All of the cable channels (and increasingly the direct to streaming events) aren’t limited by ATSC or those broadcast limitations.
Even so, the broadcast channels could easily produce in native 1080p or 4K, then downscale for ATSC as needed. Just like HD channels were downscaled to 480i for SD cable boxes.
The only limitation right now is their old broadcast equipment, and the networks not wanting to spend the money to upgrade it.
Lots of countries in Europe and Asia have native 4K broadcasting now for things like the Olympics, but not the US.