[wesk05]

Not really, to meet the HDMI 2.0 standard the cable has to be really nice with thicker wires and good EMI shielding.
Cheaper cables may not handle it properly.
BUT, it doesn't cost more than US$5 to make a 100%-capable HDMI 2.0 cable.

HDMI.org doesn't have any separate testing standards for HDMI 2.0 cables. If any manufacturer is saying otherwise, it is nothing, but to mislead/confuse/fool buyers. In all probability, a cheap high speed cable that worked fine before will continue to work fine with HDMI 2.0.