Installing a branch does not actually change the branch. I am unsure whether the user results with all packages having the proper branch or not.
I ran a pacman-mirrors -g -b testing; pacman -Syyu and it loks as if there were a few upgrades required. I am not really happy with this by I may just leave stable as the default and have the user switch to a different branch at a later time because it is a matter of if something isnt broke do not fix it.
I know I could do this within the test case of doing pacman-mirrors -g however the field I gave the system to tell it that $BOOTSTRAP_RELEASE was used did not work, perhaps an export $BOOTSTRAP_RELEASE is needed or something for it to be used later in the installation.
Cutting Edge Linux 