This week, however, the company has reversed course and says they will keep the current system in place:
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.
The whole episode was blamed on a "miscommunication inside of the [user experience] team."
Earlier this year, Mozilla announced it would be moving to a more Chrome-like release schedule, and has since moved from Firefox 4 to Firefox 7 nightly (Aurora) in just 6 months.