Cloned this story for 4.21 release notes. Need to ensure that the 4.21 release notes state that this will no longer work in 4.21.

Reference: https://issues.redhat.com/browse/CNV-57055 

The planned order of syntax changes is a follows:
4.18: [type/]name[.namespace] starting point
4.19: type/name[.namespace] preferred, name[.namespace] still working with a warning
4.20: type/name[/namespace], backward compatibility for type/name.namespace
4.21: type/name[/namespace] only
 
See https://github.com/kubevirt/user-guide/pull/871 for 4.20+