As per Howard's comments there's an easy workaround so if anyone feel strong about this it can reopen the issue.
I found it handy since more and more often i use this convention but i definitely can live without it using the workaround you suggested.
Given that, even in 5.0, the Registry is stored using a well-known context attribute name, is this change required?
The workaournd is nice. Cool you've marked this for 5.1 releases.
I think a workaround is to get the Registry (it is attribute "org.apache.tapestry5.application-registry" in the ServletContext), get the SymbolSource service, and get the symbol InternalConstants.TAPESTRY_APP_NAME_SYMBOL.
Patch against current trunk