Regarding Firefox Gtk3:
Firefox Bugzilla bug: https://bugzilla.mozilla.org/show_bug.cgi?id=627699
You can install a build on Fedora via this copr (like a PPA for Fedora): http://copr.fedoraproject.org/coprs/stransky/FirefoxGtk3/
I think the only remaining problem is Flash. Hopefully Mozilla Shumway will cover that at some point.
There are commits [1] on the Chrome tree designed to get Chrome working on Wayland, but for those commits to reach significant numbers of users will require the cooperation or at least the "non-interference" of the employer of most of the Chrome devs -- which is at this time an unknown.
[1] https://github.com/01org/ozone-wayland/commits/master