don't forget a lot of TV's are just "HDR ready" which is like when HD came count and you had loads of 720P tv's sold as HD ready. It just means the TV can handle the signal.
I saw a cracking deal on a £1000 HDR 4k TV the other day until I saw from reviews that it wasnt a HDR TV at all, just HDR ready. They really shouldnt be allowed to put HDR on a TV unless it is a proper HDR tv when they just mean its compatible. Lucklily there is the new Ultra HD Premium certified sticker which at least means you are getting a "true" HDR tv. Interestly enough ony a few HDR 4k screens sold in 2015 (the top end ones) would pass for getting this certification.
The number of "true" HDR tvs sold is pretty small I would imagine. By whether its a game console or PC, if you are running a HDR game outputted to a HDR ready TV, it wont look any different to a none HDR game.
Only HDR certified screens sold in 2016 are pretty much the genuine article (high end from 2015 excluded) so I imagine thats still a small pool