Firefox is working hard to just have one version, the current one. Firefox 9 or 10 will move the version number from the about window to Help > Troubleshoot.
When a user opens the About window for Firefox, the window should say something like "Firefox checked for updates 20 minutes ago, you are running the latest release."
It is important to say when the last check happened and ideally to do the check when the dialog is launched so that time is very near and to drop the version and simply tell them they're on the latest or not.
from mozilla.dev.usability You will probably not agree but I think this is a good change. It will help supporting Firefox because there will just be two versions that matter: the up to date version, and the old version (which is any older version).
This simplifies any solution and troubleshooting, it either works in the current version, or Firefox will update - if it's connected to the internet. Which means eventually, Firefox is always up to date and there will no old versions and therefore no issues.
Probably the biggest obstacle to getting everyone to keep autoupdate on is the bundling of crap with installers, as we discussed before.