FYI: Currently I use the Escort Passport 8500 x50, and after hearing about the introduction of KU band radar guns in the US, i asked escort about it. Here is the response i received:
I have looked into this a little more and this is what I came up with. The FCC authorized the Ku-Band for use in the US over ten years ago. We continue to hear rumors about the introduction of Ku equipped radar guns, but so far this has not happened. We have recently heard of a manufacturer producing a prototype Ku-Band gun, but so far nothing is being used for traffic monitoring. As with all other threats and new technologies, when this becomes a threat in the US we will provide a solution. Our Passport 8500, 8500 X50 and the Solo S2 all have flash chips that can be software up-dated if the police introduce a new band or frequency of radar or laser. At this time there are no new police frequencies in the US, so no up-date is required. Thanks for your interest in Escort!