https://www.cnet.com/news/ces-2019-hdmi-2-1-tv-connections-finally-arrive-cables-will-follow/

HDMI 2.1 expands on the current HDMI 2.0 connection standard, a collection of features and capabilities that allows source devices (game consoles, streamers, Blu-ray players, etc.) to send audio and video to TVs. 

For most people with current and even near-future 4K TVs, HDMI 2.1 isn't a big deal, and HDMI 2.0 is plenty. It will handle 4K resolution at frame rates up to 60 per second, and even some varieties of 8K (24 and 30 fps). It also doesn't require new HDMI cables.