TechCrunch is reporting that Firefox has inserted support for Apple's Retina display into its nightly builds, which means the official release will be in the public's hands very soon. Unfortunately, "very soon" in this case may mean "not soon enough" for many users -- while the Aurora release of this build should be out next week, the stable release might not be until January 2013. That may be too long for some users, especially since Safari supported the Retina display on day one (because it's made by Apple, of course), and Chrome released support for Retina earlier this year.
If you'd rather stick with Firefox and can't wait, though, you can get access to the "nightly build" releases (which still include features currently being tested) on Firefox's website. It's too bad we've had to wait so long for this, but diehard Firefox users will probably be happy to hear full support is on its way.