The HDMI Forum has announced a new version its audio/video specification. HDMI 2.0 boasts 18Gbps of bandwidth, nearly doubling the 10.2Gbps available in the most recent 1.4 revision of the spec. The standard has been expanded to handle 4K resolutions at up to 60 frames per second. Although the older 1.4 spec also supports 4K displays, it can't push that resolution past 30 FPS.
HDMI 2.0 has more robust audio support alongside its beefed up video capabilities. The spec now includes 32 discrete audio channels, allowing it to drive far more speakers than you'll find in even the most extravagant home theater setups. The peak audio sampling frequency has also been increased to 1536kHz, a big step up from the 192kHz typically associated with HD audio.
There are several other enhancements of note. HDMI 2.0 supports the 21:9 aspect ratio used by those ultra-wide displays that have started trickling onto the market. It also adds CEC extensions to improve control over consumer electronics devices.
Impressively, all this goodness won't require new cabling. The connector is unchanged, and according to this page on the official HDMI site, "Current High Speed cables (Category 2 cables) are capable of carrying the increased bandwidth." That probably won't stop folks like Monster from introducing ridiculously overpriced cables "optimized" for the new standard, though.
Happily, HDMI 2.0 is backward-compatible with devices that conform to previous versions of the spec.
The test specification for HDMI 2.0 compliance is expected to be released before the end of the year, and I suspect we'll see some 4K displays claiming support before then. It will be interesting to see if next-generation graphics cards adopt the specification, as well. HDMI 2.0 looks like the best way to hook up a home-theater PC.