Yea, I've been posting about this for the past few years ..
T-Mobile to Enter 600 MHz in August Posted on Jul 21, 2017 By Clive Young New York, NY (July 21, 2017)—Pro-audio RF wranglers and wireless users may be in for a surprise next month, as T-Mobile announced yesterday that it will make its first in-roads into 600 MHz next month, far head of the...
ourdjtalk.com
Ignoring the "can't use it if it's tunable outside the gap/guard bands" for a moment, there actually supposed to be 2 bands usable for unlicensed mics .. a guard band at 614-616 MHz, and a dual gap band at 652-663 MHz with unlicensed and WSD use between 657-663 MHz.
I'm going to stick with my AT3000 systems in that space for now. I have a couple mics that will work in the 500MHz space, but I like the AT3000 units and generally don't have a need for more than 1.