Backwards incompatible changes (see Bug 793924, Bug 793925) will be made to CFX to support SDK integration with firefox. Add-on builder will need to incorporate those changes of CFX to remain compatible with new versions of SDK.
The builder project has been discontinued as of April 1st, 2014.
The announcement last year: https://blog.mozilla.org/addons/2013/12/18/add-on-builder/
Next steps (still being written): https://developer.mozilla.org/en-US/Add-ons/SDK/Builder