No - "Cat 8 cable" does exist, but it's just a label that's been applied to a type of cable being made. There may be more than one company making it, and they may all be the same type of thing, but there'll be no official standard for performance, and there'll be no guarantee of interoperability between different makes of cable, plugs, sockets, patch panels, switches etc.
It's an ever-accelerating race - I expect "Cat 9" will be available soon.
I wonder, though, if people in awe of cables with GHz bandwidths ever consider that hi-def DVDs transfer at around 50 megabits/sec, and that a Cat 6a cable (500MHz) will carry 10Gbit/s?
As they sit at their PC reading the specs on their hi-def monitor, do they consider that the DVI cable between the two is capped at 165MHz?
When they tire of the Internet, and turn to watch their shiny new HD TV, do they consider that even if it has the latest 1.3 HDMI interface that's only 340MHz, and that their shiny new Blu-Ray player would quite happily deliver full resolution video and audio through HDMI 1.0 at 165MHz?
