Just like the current Lamanites/Gadiantons who are causing the destruction and scattering of the Nephites are not righteous, Mormon has no expectations that those Gentiles who will perform the parallel scattering of this currently dominant people will be any more righteous. Mormon is now looking past the historical event of the coming of the Gentiles to the events that will usher in the last days, when the Gentiles will be able to receive the book, Mormon is now writing.