XSLT 3.0 Output and Serialization: Native XSLT message

Dear list,

With XSLT 1.0 and 2.0 there is (so far as I know) no specified way of
assigning a 'native' XSLT listener to the message output from
xsl:message instructions or to the error output.

Will this change with the introduction of XSLT 3.0? If so, are there
any publicly available details on this - or perhaps this is planned
for 3.1? Does message and error listening exploit the xsl:output
declaration? Can it exploit the new streaming capabilities in XSLT 3.0
(like xsl:merge) ?

Ideally, I would like to assign an XSLT module to handle all message
and error events - this would avoid needing to shell out to C# or Java
classes using implementation specific interfaces (which just feels
wrong).

A typical use case for this would be for XSLT test frameworks
implemented in XSLT that need to test all message and error outputs
for a given input.

Thanks

Phil Fearon