Will this happen for the GPG4Win package any time soon?
Guess it totaly depends on the development of the included software, probably will take a very long time then?
I assume you are especially asking for the
S/MIME part of GnuPG.
Most things necessary for S/MIME have already
been ported to Windows.
The only major part still missing (AFAIU)
is “dirmngr” for handling CRLs.
However, there is likely quite some work
in getting the whole thing fully stable and
tested on Windows.