RPM of new major version of the browser are available in the remi repository for fedora 13, 14 and enterprise linux 6 (RHEL, CentOS, ...).
To read: Mozilla Firefox Release Notes
Installation :
yum --enablerepo=remi update firefox
Notice : this RPM is close of firefox 10 one from fedora 15/16.
This package needs xulrunner10 which install beside default one.
RPM are available for fedora 13 and 14 and, for enterprise linux 6...