HDMI 2.1 overview page has gone up, here, including a QA section. Some of the highlights.
Q: What are the support resolutions and frame rates ?
Q: What colorimetry is supported?
A: HDMI 2.1 Specification supports the latest color spaces including BT.2020 with 10, 12, and 16 bits per color component.
Originally Posted by 'Game Mode VRR
Q: Does this require the new HDMI cable?
Q: Will this work with 8K@60 or 4K@120Hz?
A: Yes if those features are implemented along with Higher Video Resolution. That will require the new 48G cable
Q: Is this primarily for consoles or will PCs utilize this also?
A: It can be used for both.
Q: Will this result in more gaming PCs connecting to HDMI displays, either monitors or TVs?
A: The intent of the feature is to enable HDMI technology to be used in these applications. Given that HDMI connectivity already has a strong presence in this area, we expect that use of HDMI technology in gaming will continue to grow.
The new HDMI2.1 specification has just been announced and it contains some really good improvements over HDMI 2.0
- Higher Video Resolutions support a range of higher resolutions and faster refresh rates including 8K60Hz and 4K120Hz for immersive viewing and smooth fast-action detail.
- Dynamic HDR ensures every moment of a video is displayed at its ideal values for depth, detail, brightness, contrast, and wider color gamuts-on a scene-by-scene or even a frame-by-frame basis.
- 48G cables enable up to 48Gbps bandwidth for uncompressed HDMI 2.1 feature support including 8K video with HDR. The cable is backwards compatible with earlier versions of the HDMI Specification and can be used with existing HDMI devices.
- eARC supports the most advanced audio formats such as object-based audio, and enables advanced audio signal control capabilities including device auto-detect.
- Game Mode VRR features variable refresh rate, which enables a 3D graphics processor to display the image at the moment it is rendered for more fluid and better detailed gameplay, and for reducing or eliminating lag, stutter, and frame tearing.
Should probably include this information in the OP to avoid confusion.
The new specification will be available to all HDMI 2.0 Adopters and they will be notified when it is released early in Q2 2017.
Tobias adds, "How an individual piece of equipment will meet the 2.1 standard will depend on the manufacturer and the features. Some manufacturers may be able to achieve 2.1 compliance with just a firmware upgrade; others will require new hardware," he says.