HDMI is related to the cable. The 2.0 specification allows for increased bandwidth required for 4k. However, an HDMI cable which meets the 1.4 specification can pass the bandwidth tabled in the 2.0 specification, which explains why existing high-speed HDMI cables do not require to be replaced.
HDCP is related to the components (hardware). In order to pass copy-protected 4k, such as movies, components require to be HDCP 2.2 compliant. Note my emphasis on "copy-protected" - if the source material is not copy-protected, for example 4k shot with a camcorder, then components do not require to be HDCP 2.2 compliant in order to view it.
At least, the above is my understanding.