This latest HDMI Specification supports a range of Higher Video Resolutions and refresh rates including 8K60 and 4K120, Dynamic HDR, and increased bandwidth with a new 48G cable.   
“We have no clear understanding of when products will be out.  Many of the HDMI Forum members have an early look at the spec so they may be working on products already.”
— Chris Pasqualino, HDMI Forum CEO
Version 2.1 of the HDMI Specification is backward compatible with earlier versions of the specification, and was developed by the HDMI Forum’s Technical Working Group whose members represent some of the world’s leading manufacturers of consumer electronics, personal computers, mobile devices, cables and components.
“This new release of the specification offers a broad range of advanced features for enhancing the consumer entertainment experience, as well as providing robust solutions to the commercial A/V sector,” says Robert Blanchard of Sony Electronics, president of the HDMI Forum. 
“This is part of the HDMI Forum’s continuing mission to develop specifications for the HDMI eco-system that meet the growing demand for compelling, high-performance and exciting features.”
Speaking exclusively with CE Pro, HDMI Forum CEO Chris Pasqualino notes, "We have been working hard to get this 'bad boy' released. We have identified the five marquee features of the new spec."
Those are:
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.

credit : http://www.hdmi.org/index.aspx