At the moment, HDMI 2.1 is the latest version of HDMI, offering the best set of features, such as support for variable refresh rates (VRR) and resolutions up to 10K.
So, if you have HDMI 2.1 devices and want to get the very best out of them, then yes, this is the HDMI version to go for, and it should prove future-proof.
However, not everyone will need the kind of features HDMI 2.1 offers, in which case HDMI 2.0 will be fine for most people.