So what's all this about HDMI 2.0 HDCP 2.2 and HDR?
HDMI 2.0 supports 10 and 12 bits worth of color information. Because 16.7 million colors cannot possibly get across some directors artistic vision...
Dual Video Streams. HDMI 2.0 allows for two video's to be displayed on one screen at the same time. This sounds weird, but is a pretty cool (and expensive) gaming feature, where people with different 3D glasses would see two different images on the same screen.
Up to 32 Channels of good quality Audio. Because 8 channels of audio is just not nearly enough for the new Dolby Atmos/DTS X experience. Surrounding yourself with speakers will surely pass the WAF.
Fixing HDMI CEC. (CEC allows HDMI devices to control one another and a single remote to control everything properly) Yeah, THAT will happen! Manufacturers will get all their stuff to interoperate reliably when happy fluffy bunnies and hyenas snuggle together happily in green flowery meadows...
HDCP 2.2 Is basically the HDCP update for 4K. So if you want commercially made 4K encrypted content actually displayed on your 4K TV, then you better make sure ALL of your stuff is fully HDMI2.0/HDCP2.2 compliant.
NO NEW CABLES! No really! Unless they have chips in them like the "Redmere" or Boosted/equalized variety, then as long as the cable is good enough to pass the data at the rate it needs to travel... it should be fine. In the real world this means, for short lengths you are probably fine, but long lengths are gonna be tough!
Who needs 4K anyway?
People don't seem to understand that it's all about where you sit. If you sit 10' from a 60" TV you simply can't see the extra resolution you get with 4K over 1080p. What 4K really does is allow you to sit much closer to a TV without seeing the pixels. So if you want to sit so close to the TV that your mother would yell at you, then 4K is a wonderful enabler...
When Joel Silver of ISF talks about contrast ratio, people listen. When he raves about it you should take notes! HDR is FAR from standardized and so each manufacturer is fitzing around in their own way, but when it works and works even remotely well, it should be a real improvement that's worth having for any serious cinephile. More about popping contrasty colors than super bright whites, HDR with 4K will finally make buying a new 4K set worthwhile.