This is the major update for Firefox on rhel & centos.
So far redhat was avoiding firefox rapid releases which made it jump from Firefox 3 to Firefox 10,in support for long term release.
Firefox 10 which has long term support has been adopted by redhat.
Rhel & centos users can upgrade Firefox packages using yum.
This does not mean that all rhel / centos users were still using Firefox 3 as there was option to use Firefox from tar was available, which is certainly more fast & reliable way to get updated Firefox than relying on dustros to release their rpm / deb packages.