MacTex Upgrade from 2015 to 2016 I wish to migrate from using MacTex 2015 to MacTex 2016 on my Mac. I have Sierra installed on my Laptop. I wish to know if: 


Installing MacTex will overwrite my old MacTex or retain it (I
actually want it overwritten!)?
If it does not overwrite, then what measures should be taken to completely remove the older version and switch to the 2016
version?


I am asking these questions since the explanation provided on www.tug.org/mactex is not sufficiently clear, and it add more to the confusion.
Installing MacTeX 2016 will create a new 2016 directory in /usr/local/texlive/ with all of TeX and friends in it. It will also update all symlinks etc. to point to the new versions. So you can run sudo rm -rf /usr/local/texlive/2015 afterwards to remove the old version. This will lead to some broken links in /Library/TeX but I never bothered with cleaning them up and they won't be used anyway.