I don't think you can really make such far reaching assertions based on the steam survey. I'm not a participant, and neither are a lot of other people, regardless of their display type. Could be people who game on TVs are less likely to be a participant. And I'd say a much larger % of 4k displays are hdmi only, not just 10%.
Yes I would guess half or maybe even slightly more than half of all 4K displays are TVs. 4K hasn't really taken off in monitors yet from what I've seen... I see a lot more people using TVs on forums when 4K comes up.
Is this bad news for AMD? It might eat into sales a bit, but overall 4K is VERY niche still. Not as big of a deal as people are making it out to be. A lot more people will be buying Fury for high refresh rate 1080p panels and 1440p.