Is it possible to use a shared "themes" folder for several sites?

In Windows 7 I tried to use a symbolic link for the “themes” folder, but Hugo does not see the themes.

Yes, that should work … But I don’t know “symbolic links” on Windows enough to answer.

There is currently a limitation in Hugo re. symbolic links for /content /static /themes/mychosentheme /data etc. This is fixed in

Which may or may not be pulled into Hugo at some point in the future.

When can we expect the next release?

I have no idea, @spf13 might.