Verses 1-3 was originally written on the outside of the scroll in its origin. This made it easy to identify the scroll in a library as it is rather cumbersome to unroll a scroll to determine its content. When the letter was transferred to codex - vs 1-3 was added to the beginning text of the letter.
I presume the point of this information is to call into question the timeliness of John's letters to the churches: as in "soon" and "at hand" are not part of the book?
If so, let's assume for the sake of argument you're right. That doesn't in any way, shape, or form negate the other verses that address the imminence of the prophecy as events that were about to unfold:
Only hold fast what you have until I come. Revelation 2:25 (ESV)
How could the church at Thyatira do this if His coming weren't going to happen for another 2,000+ years?
Because you have kept my word about patient endurance,
I will keep you from the hour of trial that is coming on the whole world, to try those who dwell on the earth.
I am coming soon. Hold fast what you have, so that no one may seize your crown.
Revelation 3:10-11 (ESV)
How could the church at Philadelphia "hold fast what they have" if He weren't coming for another 2,000+ years?
And he said to me, “These words are trustworthy and true. And the Lord, the God of the spirits of the prophets,
has sent his angel to show his servants what must soon take place.” “And behold, I am coming soon. Blessed is the one who keeps the words of the prophecy of this book.” Revelation 22:6-7 (ESV)
Revelation 22:6 uses the same words in Revelation 1:1, meaning that even if what you said is true about the first three verses of the book, it changes nothing about the writer's intent to convey imminence and immediacy.
Furthermore, how could the original "keepers" of the "words of the prophecy of this book" be blessed by keeping it if His coming weren't going to happen for another 2,000+ years?
The blessings and warnings written to those churches were meant for them, not us.
And he said to me,
“Do not seal up the words of the prophecy of this book, for the time is near. Let the evildoer still do evil, and the filthy still be filthy, and the righteous still do right, and the holy still be holy.”
Revelation 22:10-11 (ESV)
Verse 10 is a direct allusion to Daniel 12:4,9:
"But as for you, Daniel,
conceal these words and seal up the book until the end of time; many will go back and forth, and knowledge will increase." He said, "Go
your way, Daniel,
for these words are concealed and sealed up until the end time. Daniel 12:4,9 (NASB)
Daniel's prophecy in chapter 12 was meant for the "end time" and the book was sealed for that reason. John was told to leave his book open, because the "end time" had arrived. Understand what that meant through the eyes of an observant Jew of the 1st century, and the rest will fall into place for you.
It's got nothing to do with us.
“
Behold, I am coming soon, bringing my recompense with me, to repay everyone for what he has done.
Revelation 22:12 (ESV)
Another allusion to Daniel 12, this time verses 1-3.
I warn everyone who hears the words of the prophecy of this book: if anyone adds to them, God will add to him the plagues described in this book, and if anyone takes away from the words of the book of this prophecy, God will take away his share in the tree of life and in the holy city, which are described in this book. Revelation 22:18-19 (ESV)
How could any of the original recipients of John's letters suffer the consequences of adding to or taking away from the book if the events in it weren't going to happen for another 2,000+ years?
And finally,
He who testifies to these things says,
“Surely I am coming soon.” Amen. Come, Lord Jesus!
Revelation 22:20 (ESV)
Again, even if the first three verses of Revelation are only a scribe's index, it doesn't change any other verse in the book that deals with the urgency, imminence, and immediacy of the rest of John's work.
Exhausted. I'm out.