Why would it need to be updated? Either it works, or it doesn't. If you're not using the "smart" parts, then it needs to just decode the damn HDMI signal. If it stops doing that to the point of needing an update, then things are terribly terribly wrong.
It works, but there are other levels of the stack between low level decoding HDMI and the "smart" parts.
Without updates you might miss out on other improvements like decreased input lag, support for another format, and bugfixes for the existing implementations (i.e. the HDMI decoder strobes when specific configuration X is utilized).
As a concrete example, Sony added HDR to one of their lines a year after it's original production a few years ago[1].
