[plt-scheme] whither units?

I was thinking about units today, and browsing through the list
archive I came across this comment from 18 months ago:

  Date: Mon, 18 Nov 2002 08:37:04 -0700 (MST)
  From: Matthew Flatt <mflatt at cs.utah.edu>

  [Side note for those interested in units: Expect a re-design of the
  unit forms in the very near future.]

How near is "very near"?  :)

I like modules because, for instance, a macro can figure out the
origin of a module import (with `identifier-binding').  It can't
figure out the origin of a unit import, though, because units are
run-time values (and in fact just macro-expand to lambdas, more or
less).  It would be nice to have an expansion-time entity like a
module that is parameterizable like a unit.  Is this where the
re-design was headed?  Is it headed there now?  Or anywhere?

--dougo at place.org