XSLT 2.0 extensions? Function memoization.

On this list it has previously been stated that adding extensions for
XSLT 2.0 would be postponed until the long list of 1.0 extensions were
implemented (or something like that).

Has this been achieved yet? I would like t re-introduce, in a modified
form, a proposal that Dimitre Novatchev originally requested for
memomizing xsl:functions.

The modification being that the memoization reqest be an extension
instruction actually present within the xsl:function concerned (this
seems to me necessary to preserve compliance with the specifications -
user-defined data elements and extension attributes may not cause a
different final result tree to be produced, and, in some cases,
memoization of a function will do just that). 
-- 
Colin Adams
Preston Lancashire