But wait, you just wrote it up there. Harmattan is Qt, with GTK/Hildon marked as deprecated (it's still there but don't build empires on it).
GTK+/Hildon won't be used by the applications shipped with Harmattan out of the box and therefore won't be pre-installed. When we say that GTk+/Hildon will hopefully be there as community supported we really mean that. If all things go well developers interested in these libraries would find them in Extras, just like they are finding e.g. the Python bindings there now.