The maximum physical bitrate of 1.4a supports 4K/30fps in 8 bits, but only 24fps in 10bits which is required for HDR. Maybe it's possible as long as they are stuck at 24fps.Does not compute, since HDR will be supported on slim and fat with a fw upgrade...... Is it the combo of 4k and HDR that does not work over HDMI 1.4, then?
But it doesn't matter, without HDCP 2.2, no content provider will allow 4K. Case closed. I seriously doubt it's possible to implement the new crypto by a firmware update, no matter how flexible their display controller is, these things are secure by virtue of full hardware implementation.