I've been thinking about exactly this, and doing some preliminary
planning with pair of Wikipedian educators. If done right, Wikipedia
MOOCs could really move the 'active editor' needle and bring in a new
generation of 'natural-born Wikipedians' for whom it hasn't been as
easy to dive into Wikipedia as it was 5 years ago.
At this point,
it seems like Coursera is the only MOOC platform that has the
technology to do the sorts of peer evaluation that would be necessary
for running a Wikipedia course with thousands of students; it has a
number of humanities and arts classes, as well as open-ended technology
classes, where all the grading is done by peers. I've taken one class
that had peer grading, and it was--if not smooth--at least usable for
peer evaluation.
Unfortunately, Coursera professors have to be at
universities that are signed on with Coursera at the institutional
level, which means that bureaucratic and political barriers will be in
the way unless the professor is already at one of the participating universities.
If any professors on this list have a strong interest in doing a MOOC with a Wikipedia component, let me know.