I was raised in a Dutch Reformed church that joined the UCC. At the time I was in Sunday School, the mainline churches all had confessions or creeds that defined them. 50 short years later - all gone. Dust in the wind. Even the Episcopalians, who thought apostolic governance was security - finished.
The collapse of the seeker movement is upon us. Rick Warren and Bill Hybels were not fruitful. Leaders, but not fathers. Mars Hill was a flash in the pan.
You Catholics beware. Your model is the strongest but it will not survive an antipope with Facebook. The old antipopes has short lives and limited reach.
Jesus, as they say, calls us oer the tumult.
To be replaced by what?
The issues are different to the infiltrators of the 21st Century to those of the prior century, but the ends are the same, to destroy active, witnessing and Biblically based churches from within. The "seeker sensitive" movement, the prosperity gospel, post-modernism, etc., are the wedge issues used by the modern equivalents of Rauschenbusch, Niebuhr, and Fosdick, to infiltrate, neutralize, and destroy evangelical churches.