Default value like property 'version' at 2.0-alpha-3

If I define a requiredProperty at archetype-metadata.xml without a defaultValue (example: <requiredProperty key="copyright"/>), the value of the property is prompted when I run mvn org.apache.maven.plugins:maven-archetype-plugin:2.0-alpha-3:generate. If I input nothing (just hit an enter), the process fails.
If I define a requiredProperty at archetype-metadata.xml with a defaultValue (example: <requiredProperty key="copyright" defaultValue="Basegen 2008"/>), when I run mvn org.apache.maven.plugins:maven-archetype-plugin:2.0-alpha-3:generate the value of the property is not prompted anymore and process assumes the defaultValue.
I wish a way to the command mvn org.apache.maven.plugins:maven-archetype-plugin:2.0-alpha-3:generate prompt a value to the requiredProperty and a default value is assumed if nothing is typed (just hit an enter). At version 2.0-alpha-3, this happens with property 'version': if i just press enter, the process assumes the value '1.0-SNAPSHOT'.