Mozilla's web page https://wiki.mozilla.org/Addons/Extension_Signing "If implemented on ESR, the first version to support signing would be Firefox ESR 45. The current plan is to have ESR work like 40, with a preference that can turn no enforcement, but that may change in the future." This is opposite on what I found in the attached email from the Kalpy Consulting in the last section. Past experiences, Mike Kaply was accurate for all Firefox updates. "Important Dates August 11, 2015 - Projected release of Firefox 40, Firefox ESR 38.2. Firefox 40 will warn about add-on signing. EOL for Firefox ESR 31. September 22, 2015 - Projected release of Firefox 41, Firefox ESR 38.3. Firefox 41 will disable unsigned extensions unless a preference is set. This preference will be removed in Firefox 42."