The HDMI version jumped from 1.4 to 2.0 for some reason. Makes you think big changes were going on! So what's new?
They've increased the bandwidth from 10.2Gbps in HDMI 1.4 to 18Gbps in HDMI 2.0.
Higher 4K resolution FPS rates. HDMI 1.4's maximum (only) 4K frame rate was 24 FPS. HDMI 2.0 supports 50 and 60Hz frame rates. Because we really need to see at home "ultra real" high resolution videos like that high frame rate version of "The Hobbit"?
More possible colors. HDMI 1.4 was limited to 8-bits. 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... Oh, and wake me up when they actually have content available?
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 apparantly a very cool (and undoubtably very 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 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...
NO NEW CABLES! Thanks, HDMI. Everyone else gets to ride on the HDMI 2.0 gravy train except the Cable manufacturers....
One down side to HDMI 2.0 is that NONE of these features are REQUIRED to be supported by a HDMI 2.0 device. So just because you buy a 4K TV that is HDMI 2.0 doesn't mean it will support 4K at 60Hz. et cetera...
HDCP 2.2 Is basically the HDCP update for 4K. So if you really want 4K and want to see 4K source material that is encrypted (anything not home made) then you better make sure all of your stuff has HDCP 2.2.
Easy, just get something with HDMI 2.0 since obviously THAT will have HDCP 2.2... Nope! Having HDMI 2.0 does not necesarrily mean having HDCP 2.2! So you could have a 4K TV capable of 4K at 60HZ, but it might not be able to display your 4K Blue Ray movies at that resolution (or maybe any resolution) in the future.
So what to do if you want to build a 4K capable system? Sometime in 2015, or perhaps 2016, all the pre HDMI 2.0 and pre HDCP 2.2 equipment will work its way through the pipeline and you'll be able to "safely" assemble a true 4K system. Until then, be very, very careful what you buy if 4K is the eventual goal.
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...