For folks new to this blog, read previous comments on Power Mac Internet security here, specifically discussing OS X and built-in apps, and a little bit more here.
I am working on the Fx15 port a bit early, which is being bogged down by the MPL license change invalidating many of our patches and DOM event changes requiring some big surgery to widget/. More on that later. However, we are still on schedule for an Fx14/10.0.6 release around July 13, and Classilla users will also be happy to hear that several major security flaws have been eradicated from 9.3.1 so far; the audit is now almost to the Mozilla 1.8 era and the review process should get faster then as many of the flaws will start to cover code that doesn't exist in Classilla.
As far as Firefox itself goes, no decision has been reached so far about 10.5 support. You'll be the first to know.
BTW: 100th post!