It is crystal clear that over the last few decades, Christianity's centre of gravity has relocated from the Global North to the Global South. While church buildings in Western Europe are being closed, or rather sold, new mega-churches are filled with believers in Africa, Asia, and Latin America. Charismatic and/or Pentecostal movements practice the Christian religion in dynamic and innovative ways, changing the narratives and challenging the established churches and society at large on all continents. The Global Southern, or non-Western, missionaries are rapidly taking over the Global Northern hemisphere for a reverse mission for the purpose of salvaging the perishing souls, particularly in the Global North, which seems to have departed from its glorious past. Thus, the main thrust of this work is to critically and scholarlyly examine the current trends in demographical changes in world Christianity, their implications for world Christianity, and possible solutions to the declining status of Christianity in the Global North to save it from going into extinction. This study makes some recommendations and suggests that they might help to engender fresh thinking and better planning in order to respond sensibly to the current challenges and to cash in on the opportunities provided by the Global South phenomenon. The paper concludes by calling for an organised reverse and rescue missions in the Global Northern hemisphere before it is too late.