> If they want C++, I don't see why they don't just use C++.
C++ isn't trivially portable and has various other issues. Regardless, at this point in time it would be better to use an even higher-level language. The natural candidate would be Vala, of course.
A combination of Vala and the related projects of GNOME-introspection, automatic bindings generation, etc., for higher-level languages on top of that, would have been a compelling target for GTK3.