I just launched Inkscape, and noticed the port seems to be done! In Fedora 26, they ship Inkscape 0.92 which uses Gtk+ 3.
0.92.x does not use gtk3 (there is an experimental compile flag to use it, but it's still experimental)
You're both right. Fedora enables this option on F26.
rpm -qa | grep inkscape
inkscape-0.92.1-4.20170510bzr15686.fc26.x86_64
ldd /usr/bin/inkscape | grep gtk
libgtkmm-3.0.so.1 => /lib64/libgtkmm-3.0.so.1 (0x00007f12a6a2f000)
libgtk-3.so.0 => /lib64/libgtk-3.so.0 (0x00007f12a4dbb000)
Visual Studio for Mac is also Gtk 2.x, but they (Xamarin at the time) invested heavily in a custom Gtk fork as much of the hacks were not suitable upstream.