NVidia has to refuse to adopt HDMI2.1 if they don't want their GPUs to have a built in free alternative to G-Sync. They can probably hold off adoption for a year or so(Doesn't look like they'll have any truly new gaming GPUs in that time given Volta is just a compute-orientated spin on Pascal) but likely not much longer than that. Like many of NVidia's "features" past and present it will soon be destined for the history books due to their proprietary nature(And general lack of reason to have ever existed in such a form).