Do we know if there's going to be a Mac version of the flash tool?
The impression from Planet is that that's very unlikely, unfortunately.
Still, even though very awkward, it is at least
possible to flash from a Mac, by booting into Linux. Having done it once, I've kept the Debian 9 USB stick, and another stick with the Flash Tool &c, for precisely this eventuality — so although it's a pain shutting everything down and rebooting, the flashing shouldn't take too long.
And it shouldn't be needed very often. If comments above are accurate, this is the last time it'll be needed for a simple firmware update; after this, we'll only need it to change the OS.