When you apply the license for Workstation pro, I believe the VM will continue to run. If the license expires, the VM cannot be powered on again. I think I am missing something in the question. Could you rephrase the issue again
Upgrading/uninstalling/etc of the application will have no affect on any existing virtual machines. To your host, the VMs are merely files/documents. Think of it like upgrading Microsoft Word from Word 2003 to Word 2019. All of your Word documents remain untouched.
Workstation Pro also includes the Player UI if you want to run it in the same UI you are used to using, and can still be launched after the 30-day trial for Pro expires.