I'm sure there are others on this list who know better than I the
content's of Plenum's COLLECTED WORKDS OF LSV. But from my experience it
looks as if they do contain everything or nearly everything -- at least,
they contain an awful lot that English-speaking folks have had no access
to. The English Volume 3 (Russian Volume 1), for instance, contains
Vygotsky's prefaces to many classic psychological books (Kohler, etc.),
which are extraordinary for their philosophical incisiveness.
As to your question about THINKING & SPEECH (apparently the more accurate
translation of what was called in English THOUGHT & LANGUAGE), a new
translation does appear in the first English volume of the COLLECTED
WORKS, I think, which must now be about 10 years old. MIND IN SOCIETY is
of course a collection of essays, and I would imagine that all these
appear somewhere in the COLLECTED WORKS, but probably not together.
Stanton Wortham