There will not be a Pro of Beta. When Zorin OS 17 is officially released and no longer in the Public Beta Testing phase, the ZorinGroup will introduce the Direct Upgrade Option Update for Zorin OS 17 which will enable users to either upgrade the Zorin OS 17 Beta to Zorin OS 17 Pro or users to directly upgrade from Zorin OS 16.3 to Zorin OS 17.
It is advised that users perform a fresh reinstall of Zorin OS 17 upon its official release, however.
Beta Testing can potentially introduce some significant changes.