The panels are 4k pixels and are 120hz refresh rate capable, they have been for a while.
The issue is not the panels but the connectors into the TV/Monitor. TVs do not come with DisplayPort, supposedly because of DRM reasons from what someone in the industry told me. TVs only come with HDMI, and no TV has an HDMI port capable of 120hz in 4k resolution. If they came with a DP1.4 input then they would be able to do it, but such a thing doesnt really exist. Only a handful of computer monitors have that sort of connection. The Wasabi Mango model mentioned in this thread is one, as are the new $2000 Asus and Acer model GSync monitors. They are not TVs however, they are just computer monitors. No actual TV has a 120Hz capable HDMI port.