4k broadcasts will be very rare. I can see these stations doing the same thing as now. Multiple bandwidth stealing sub-channels, except they'll be in HD.This is the key... all the channels in an area on ATSC 3.0 are all on the same transmitter, however within a few years they will move off onto their own transmitter which will open up a lot... lot more space so channels can do 4K and other things with their signal.

