Of course, the text of Revelation itself does not specifically say the descriptions of the churches are written as history in advance. However, when eminent church historian Philip Schaff lists the major trends of church history, he describes them in terms remarkably similar to the language John used to describe the seven churches.
As Jesus through John writes to the seven churches, John is performing a prophetic ministry to counter the work of false prophets he sees influencing his churches in the first century.
As a prophet John is able to point out their departure from the faith, and predict what will happen to them as a consequence. We will see that what he has written to each church in a prophetic sense reaches beyond the first century.