The high tide of Protestantism really is over. The heterodox “half” (~80%) wil continue to drift into liberalism and atheism, and the orthodox “half” (~20%) will eventually convert to Orthodoxy or Catholicism. And some leftovers will remain in minor Calvinist or Charismatic sects. That is what is already happening and what will continue to happen this century.
To add to this, I hadn't heard any of the arguments that Dr Bob had made before and thought they were interesting; but they ultimately rely on his presuppositions of the ultimate authority of the Bible and then predestination and Sola Scriptura. One thing that has happened with all of the Post-modernism and wokeness, is that people can directly see similarities between how these philosophies have drastically changed what was once considered "American" or "Western" and how what is considered "Christian" has drastically changed in many of these Protestant (and really, all) denominations.