Hi Mike,
There's a great
thread in the Wireless forum about the 600MHz auction, which has been in effect for some time now. At this point, manufacturers are prohibited from making or selling any system that operates in the 614-696MHz spectrum (other than the guard band and duplex gap), and retailers are no longer permitted to offer any of the same for sale in the US.
The trigger, though, is that if a system is able to be tuned to an illegal frequency, it has "lost its type acceptance" with the FCC, and is no longer permitted to be used. So, a system, even if you can tune it to a legally-allowed frequency, the fact that it can be tuned to an illicit frequency prohibits its use.
The time frame for everything is from now until July 2020, where use in the affected spectrums will become officially illegal. At this time, you can still use it, but you run the risk of the newly licensed users interfering with your operations (and you are not permitted to interfere with their operations).
Shure's Mail In Rebate for affected systems ended October 31, 2018. Sennheiser's is still going a bit longer, but will eventually end as well. A company I work with had a bunch of J50 QLX-D channels that they got a firmware update for from Shure. Not sure if that's a widely available update (updated to J50A, IIRC) or limited to larger users of the systems. Either way, if you have a system in the impacted spectrum, I urge you to get it replaced or re-tuned as soon as possible!
-Ray
