Speaking of ports, i was reading the comments on the GTK2 to GTK3 port bug in FF and as it seems it started to compile. Its rough though according to the comments.
Nah, the majority of firefox is platform and toolkit-independent. It does some drawing through Gtk2, but only on Linux.
Like people say, proof-of-concept ports to Qt were made many times, but never mainlined, so they died without corporate backing.