Yes the letters were addressed to 7 specific churches however, they were not the only churches at that time. These letters were written to all believers to encourage, rebuke and warn them of what God requires in His Church. I believe you are correct in that there is a representation present today of individuals who could be best characterized by both the Smyrna and Philadelphia churches, if not all the 7 churches throughout the Church Age. I do agree with the author of this chart that each time period could be best described "overall" by one of the 7 churches. Today the churches are a mixed multitude but "overall" The Church is basically lukewarm in comparison to other time periods. The messages to all the churches are very relevant today as we are drawing closer to the end of this age and The Church of Philadelphia is the best example of those approved of by God at this time and more important - to be prepared as His Bride.                     (answer to question regarding the seven churches addressed in Revelation) see attachment
Doug L