All this clearly indicates that Judaism does not recognize a permanent change in status away from the Jewish people. A convert reverting to another religion would be considered an apostate.
We cannot, of course, deny individuals the right to adopt a religion of their choice. They have the freedom to adopt Judaism and the freedom to leave it. For all practical purposes, they will then be outside the Jewish community(in contrast to Bek. 30b), but we would always be willing to accept their return to us. Their children too, will have full rights as Jews , should they wish to exercise them.