** Please people, this question is not meant to begin any flame war. **
I am trying to understand what happens to existing libraries implementing some functionality when the same functionality that was not previously there in the language now comes in as part of the language? For e.g. C++ would soon have std::thread as part of the language standard so what happens to the POSIX or Boost Libraries?
I would also be keen to understand what experiences users of other programming languages might have in this regard.
C++ std::thread is in large parts based on boost threads. So boost threads will never really disappear, they will live on in the standard C++ library.
Additionally, on many platforms boost threads use posix threads as backend, so they will never disappear too.