wxWidgets supports not only GTK, but also now Qt and X11 (as well as Motif, but that's deprecated). It would be nice to support using at least wxQt instead of wxGTK, so applications are more native in a Qt environment. Not sure if this would be ideally implemented as a WX_SINGLE_TARGET USE-type thing (to choose per package), or just a rename of x11-libs/wxGTK to something generic with exclusive USE flags for how to build it.