The reason behind this seemingly about turn? It seemed that members of Mozilla’s Bugzilla forum did not find this move to be of any benefit, and raise plenty of hue and cry in the process. I suppose Mozilla has heard their complaints which were loud enough, having the better sense to keep users happy by abandoning such a plan. Below is an excerpt from Alex Faaborg, Principal Designer on Firefox.
Just in case this got lost amongst the many threads in progress: there are no plans to adjust the version number. It will remain in its current place in the about window, and we are going to continue with the current numbering scheme.
An attribute of working entirely in the open is that we sometimes create significant confusion as we discuss design work that is in progress. However the bright side is that there is never a shortage of feedback :)