The HDMI Forum's Technical Working Group has released the specs for HDMI 2.1, as well as a new Ultra High Speed HDMI cable. Some of the 2.1 spec's features will be backward compatible with your existing HDMI 2.0 cable, others will require you to upgrade.
High bandwidth content, resolutions and dynamic HDR
The new spec opens up super high bandwidth content like massive uncompressed 8K resolutions at a 60 Hz refresh rate, or 4K vision at 120 Hz. The total transfer rate jumps from 18 Gbps in the old spec to a whopping 48 Gbps in 2.1.
The spec supports higher resolutions as well – up to 10K/ at 120 Hz – but in order to fit that much data down the pipe, it applies a Display Stream Compression algorithm.
I don't hear a lot of people complaining about the low resolution and pixellation of their 4K TVs; this is more likely aimed at commercial massive-screen applications, as well as potential VR gear where images take up your entire field of vision and are split in half for stereoscopic view.
Depending on your resolution and frame rates, HDMI 2.1 also supports Dynamic HDR, which can display a wider range of colors and tones, and adjust each scene, or even each frame, for optimal depth, detail, brightness and contrast.
Refresh rate upgrades
There's some new features around refresh rates as well, which will be particularly interesting to gamers.
Variable Refresh Rate (VFR) can constantly change the refresh rate of a screen to match the video output device. That means that as your PC gaming rig's frame rate goes up and down, the screen syncs immediately to the current frame rate for the best possible smoothness. Motion is enhanced, lag, stutter and frame tearing are reduced or eliminated and the overall experience should be better.
Quick Media Switching (QMS) for movies and video eliminates the blank screen wait period before content is displayed when you're switching between HDMI devices.
Quick Frame Transport (QFT) reduces the latency between output and screen, to eliminate lag in online and offline gaming.
Audio
Audio gets a kick up the backside as well with the eARC bi-directional data channel, leaping from a 1 Mbits/sec pipe right up to 37 Mbits/sec. This allows uncompressed 5.1, 7.1 and high bitrate audio streams like Dolby Atmos, DTS Master, TrueHD and DTS:X.
Lip sync correction is now mandatory, and as with the previous spec, the TV can power the sound system on and off, as well as muting and controlling volume.
Meet the new Ultra High Speed HDMI Cable
While some of the HDMI 2.1 features will work using a current HDMI cable, the high bandwidth stuff will require a new cable, which should become available through various manufacturers in the first half of 2018.
The new cable is compatible with type A, C and D connectors, and it supports the HDMI ethernet channel. It's backward compatible with all previous devices, and the maximum length for a passive cable will be somewhere between 2-3 meters. Active cables are supported by the spec for longer range applications.
Source: HDMI.org
I'm watching content on a 75" 4K at about 3m distance and I'm pretty sure I can't even remotely see the individual pixels being displayed on the TV. Tripling or even just doubling the resolution of that would come with diminishing returns that just don't make sense, to me.
When you have a +13 ft long projector wall... such as resolution will be a huge impact. Even more so, with larger sizes... such as projection to an outdoor setup, and or actual theatre (Imax style) screen.
Also, if content is in 3d... at 10k resolution... thats 5k per Eye image. Which isnt much a step up from 4k, in all actuality. And man... a true HDR Laser projector... in stereoscopic glory, on a larger screen?! That is going to be Damn amazing.
A former friend had an Optima 720p projector that used 144hz? for the 3d glasses... and his 13 foot long screen, and us about 15 feet or so back... was mindblowing. It actually was pretty much the same as the Imax experience. I never thought that would be possible. Images were crystal clear... and closest images came within maybe 4 ft away from your face.
He played the original the Predator film, that was recently converted to 3d... and I could not believe it. It looked as if it was actually filmed with 3d cameras. I felt like I was actually in the Jungle with the characters... and I was like... staring at the details in the tree leaves... rather than watching the actual actors! lol I can only imagine the higher resolution + HDR! =]