State of SDL_mixer and audio capture

When will SDL_mixer’s API be rewritten for SDL 2 (adding stuff like
per audio device mixing (making Mix_OpenAudio archaic) and possibly
changing what the 1.2.15 (or whatever) documentation says about
functions that don’t check for NULL arguments for its 2.x
equivalents), and when and how will audio capture be implemented in
SDL 2? Are these things already done? Really interested in knowing
about these things so that I can either start reintegrating with
SDL_mixer, waiting, or implementing my own audio mixing.

Also, although I didn’t read the documentation for those functions, I
don’t get why there are separate mixer functions for music.