HD came around in 2006 with Sky, UK went 1080i min. for main stream but SD feeds did keep going for ages (and still do). But yep, BBC 2 Wales only just went HD (last few months?) but that is the pipe in the back haul, kit bolted on etc. and the cost. HD was also seen as a revenue stream by some providers. 4K will get the same and indeed it has with disk.
4K seems to be shifting TV's faster than HD did back in the day and a bigger driver. Reading various industry docs. Also you get full 4k capable sets compared to the "HD Ready" fudge.
PAL was there for 50 years. HD 2006 (UK 1080i), 4k last several years, 4? 8K on the horizon, things are moving quicker and I think the industry is slow to capitalise on it but they will mess it up.
I am dropping 4k on Netflix as the quality is down on what it can be, HD is far better for me personally (I can see the issues and once you have your eye in, it drives you bonkers), Apple TV and BT sport are superb at this. (not having Amazon or Sky to compare).
Gaming is something I have missed, for some ungodly reason I stuck with the iMac and Mac does not do gaming. Playstation Pro for me soon.