See this recent thread, on problems running in 4k/being limited to 2k in some situations. As there if it‘s something you need definitely raise it with Harman, the more people raise it, or vote for it, the more likely they will look at it.
I can see one definite use case for this. Just this year digital advertising boards have appeared in our town, in shop windows and bus stops. They are basically HD TVs on their side, I am not sure exactly what resolution but I think at least 4k so they look as good as posters from quite close up. And AIR with Starling and Feathers is a good tool for creating such adverts.