Forget 4K, HDMI Specification 2.1 supports 8K and 10K resolutions
The new HDMI Specification 2.1 features resolutions of up to 10K, as well as 8K@60fps and 4K@120fps.

The new HDMI Specification 2.1 features resolutions of up to 10K, as well as 8K@60fps and 4K@120fps.