Cisco recently released 17.12.4 for the 9800 Controller and we are now able to support both WPA2/WAP3 clients using the same SSID without using transition mode. The only issue I found was the older clients were not really happy with Fast Transition (FT) enabled so I have disabled at the moment pending more testing.
I have been able to test this SSID with an assortment of devices in the house, everything from Google Assistant devices, legacy Roku, and some newer devices.
Checking a couple of these clients, I can see the WIFI 5 devices are working with WPA3 while the WIFI 4 devices are falling back to WPA2. This makes this a great way to start migrating your environment to support 6 GHz as WPA3 is a requirement. You will also get feedback on devices which show up as 6E capable making it easy to understand how many devices in your enterprise are 6 GHz ready. Long term this is a great step toward getting enterprises using older APs ready for 6 GHz and WIFI 6E\7.