3.1.12 I am currently tracking testing (jessie). What will happen when a release is made? Will I still be tracking testing or will my machine be running the new stable distribution?
It depends on the entries in the /etc/apt/sources.list file. If you are currently tracking testing, these entries are similar to either:
deb
http://ftp.us.debian.org/debian/ testing main
or
deb
http://ftp.us.debian.org/debian/ jessie main
If the third field in /etc/apt/sources.list is 'testing' then you will be tracking testing even after a release is made. So after jessie is released, you will be running a new Debian distribution which will have a different codename. Changes might not be apparent at first but will be evident as soon as new packages from unstable go over to the testing distribution.
But if the third field contains 'jessie' then you will be tracking stable (since jessie will then be the new stable distribution).