I'm still not getting the firefox-38.1.1-1.el6.centos.x86_64.rpm that was announced yesterday (8 August) morning. I looked at several of the mirror sites I receive, and they all have the new firefox in their Packages directory, but their repodata is all a day older (7 August), so yum doesn't see the update.
Example mirror: http://mirror.cs.uwp.edu/pub/centos/6.7/updates/x86_64/