I've had a Panasonic TX55-CX802 4K TV for about 18 months, and I've been very happy with it, sourced from sky Q UHD, HD, and blu-ray...
Recently I received an HDR firmware update for the TV, this provides an HDR option on each of HDMI inputs, unfortunately the on board apps are still limited to 4K however.
I've been using a ChromeCast Ultra to stream BT Sports ashes coverage to my tv, one can also cast from youtube...which contains some 4k HDR videos.
WOW! What a noticeable improvement over 4K, the colours, the resolution...so lifelike
So now I've just acquired an ultra HD blu-ray player (UB900), with HDR (for Netflix too)...the HDR blu-ray version of Planet Earth II is stunning!!!
Definitely worth taking HDR into account with regard to future proofing...
FYI There are as yet no plans for HDR for Sky Q, but I'm sure they'll have to implement it at some point...in order to compete with Amazon and Netflix