I hope this is not belaboring the obvious, but have you used Science
Citation Index (or the online equivalent) to look for recent papers citing
the earlier work you are focusing on? That's one way to capture a stream of
research (in addition to the natural one of asking people, which you have
done). I don't know what resources you have, but your library should be able
to help with the search, one way or another.
Kate McCain "bibliometrics R us"
College of Information Studies
Philadelphia, PA 19104
mccainkw at duvm.ocs.drexel.edu