And when THEY apostasize and split, forming smaller and smaller "orthodox" bodies, each of them will proclaim that only THEY, according to THEIR private interpretations of the Bible, are remaining faithful.
That may be oversimplifying the situation and history of the Lutheran Church. Historically, for example, the WELS, WIsconsin Evangelical Lutheran Synod was merely under the umbrella of the Lutheran Church of America but it already existed prior to their joining to be in a sort of solidarity with Lutherans in general. http://en.wikipedia.org/wiki/Wisconsin_Evangelical_Lutheran_Synod
All the same, it is very different than how the Catholic Church might be which even at that, seems to have a split from the Orthodox.