Well, in my music history class, our professor was talking about different
countries' terms for operetta: "Opera Comique" in France "Opera Buffo"
in Italian, and he mentioned in passing that most modern musicals, with
exceptions of things like Evita and Les Miserables because they have no
spoken dialogue, are in the same form.  So, if you're asking about musical
STYLE, then probably there aren't any (or many, so as not to generalize too
much) new operettas being written.  But if you're talking about musical
FORM then new ones are being written every year.

Maria Holub <[log in to unmask]>
http://www.geocities.com/Vienna/Opera/3774/index.html