Apparently, since 2010, not much.  But it looked really interesting and almost ready back then:

  - go to channel9 on msdn.com and search for "translating telephone"

  - research done by Kit Thambiratnam with Frank Seide

I want to do something similar:  perform speech recognition on conference calls while they are happening, display the transcript to each participant in the conversation, optionally display the transcript translated into another language.  Can it be done in Lync?

There is no such feature in Lync 2010 or 2013 out of the box, but a custom solution may be developed through Lync managed APIs.

http://msdn.microsoft.com/en-us/library/lync/hh228139(v=office.14).aspx