The key word in this verse is “soon”. When God’s Holy Spirit inspired John to write these words, they were written to the seven church’s along a Roman postal route. Certainly God intended future generations to read these words and the words certainly have meaning to all generations beyond John’s but this fact cannot discount or eliminate altogether the importance they bore to that generation and those church’s. A few years after John wrote this letter God destroyed the Temple, all of its contents, and all that was done and accomplished in the Temple on a daily basis. This destruction came through the Romans in the year 70AD. He reveals in John’s letter the mystery of why He will be doing this and He is revealing this directly to John. The events described in John’s revelation are a good and accurate description of the events of 70AD and the timeframe certainly fits the description of “soon”.
Centuries earlier, God gave a similar revelation to Daniel (Daniel 2:27–45). This was a direct revelation to Daniel in the same way John’s revelation was direct from God to John. In Daniel’s revelation, God revealed many things to Daniel. Some things were to happen in the near future (while Daniel was still alive), while others were to happen in Daniel’s distant future. God’s revelation to John was a more detailed account of those things which were to happen in John’s future. In John’s vision, God omitted those things of Daniel’s vision which had already happened.