Nathaniel and I have been discussing this for some time offline. I plan to
obtain the actual ISO10646 documents once they are released and review
them with an eye towards including information about this in MIME. We'll
make the decision as to whether a separate document or some additional
information should be added to the base RFC at that time.
My understanding is that 10646 is approved but there were some comments that
had to be fed back into the process. I don't think the final documents are
available just yet (if someone knows otherwise please let me know), but
they're due out any time now.
Ned