While 4K proponents would have you believe that its success is just around the corner, survey results from the Leichtman Research Group show just how far it has to go – as HDTV penetration for US homes has just reached 81%, some 15 years after first launching in the market. The good news is that this figure is up from 46% five years ago, and the portion of homes that own more than one HD set has risen from 17% five years ago to 52% today. There seems to be a strong link between HD-readiness and pay TV subscriptions, as 89% of those homes with a single HD set are also pay TV customers, climbing to 91% in homes with…