The Register reports Mozilla has made the removal of version numbers in Firefox a long-term goal:
Asa Dotzler, director of the Firefox product at Mozilla was the chap who started the thread on Bugzilla that mentioned removal of Firefox version numbers from the About screen. That post generated heated debate, with suggestions that it is simply change for change's sake and it could confuse users trying to look up version numbers in order to troubleshoot problems.
Dotzler told The INQUIRER, "There's been some discussion around removing version numbers from the Firefox 'About' window. Our goal is to avoid confusion and make sure users always have the most current version of Firefox. While that's the long term goal, this change isn't happening overnight. Right now, the version number is available in the Help-Troubleshooting menu."