In repositories (Index of /repositories/mozilla/openSUSE_11.1/i586) find newer Firefox:
MozillaFirefox-3.0.5-2.3.i586.rpm 30-Dec-2008 22:01 894K

but whynot can I NOT update it?

Yast bush only older version...
Mozilla Firefox Web Browser 3.0.5-2.2 (3.0.5-1.1) 3.2 M