I was wondering why my firefox automatic update feature hasn’t told me the availablility of the new version of the browser. This article answered my question. It turned out that there’s still a version 1.5.0.8. This new version is mainly to give you the option to decline major upgrade.

Firefox users expecting their browser to automatically install version 2.0 may have to wait a little longer. Firefox’s automatic update feature does not presently give users the option of declining an update. […] Firefox will first ship a 1.5.0.8 upgrade to the browser that will give them the ability to decline the major upgrade. After that it will push out the 2.0 version via automatic update.