can I update the Zorin OS 16 network manager to a more recent version in advance of the appearance in order to be able to use the wpa3 WiFi encryption?
Unless I am mistaken, the Zorin 16 network manager should be a version that supports wpa3. It needs to be a version above 1.16.
The current Zorin 15 version is 1.10.6
When Zorin 16 is released, ensure that Secure Boot in your motherboard is disabled and the wpa3 / wifi should work ‘out of the box.’
If you are asking if it is possible to upgrade the network manager on Zorin 15 prior to the release of Zorin 16, sadly, it is not. Even if you use the Focal or Disco repos to try to install it, you will run into integration problems.