I affirm that, of course, the canon is closed. But beyond that, there are those who use Revelation to prove that the gift of prophecy must have gone extinct, because of the dark double curse found in Rev 22:18-19:
For I testify to everyone who hears the words of the prophecy of this book: If anyone adds to these things, God will add to him the plagues that are written in this book; and if anyone takes away from the words of the book of this prophecy, God shall take away his part from the Book of Life, from the holy city, and from the things which are written in this book.
It is said that, since Rev 22 appears at the very end of our Bibles, it can only mean that it is the very end of divine revelation!
This is to take Rev 22 out of context, and approach it with shallow exegesis. Rev. 22 speaks of the book of Revelation and that’s it, using the custom of cursing the scribes who badly copy a book. And well, there is nothing to indicate that the Apocalypse was the last written canonical book, it seems that way because it is the last in our Bibles, but in the ancient manuscripts not necessarily.
Let’s begin with the term, “this book”. In Revelation 22 it is clearly a reference to the book of Revelation!
22:8 Blessed is he who keeps the words of the prophecy of this book.” Revelation itself is the book of prophecy, in a way that 2 Kings or Romans or John are not. See too v. 9.
22:10 Do not seal the words of the prophecy of this book (Revelation), for the time is at hand.
The passage can and should be understood in this fashion:
For I testify to everyone who hears the words of the prophecy of this book of Revelation: If anyone adds to these things, God will add to him the plagues that are written in Revelation; and if anyone takes away from the words of the book of this prophecy, Revelation, God shall take away his part from the Book of Life, from the holy city, and from the things which are written in this book of Revelation.
Besides a close examination of the context, we are also need to look at the literary context. someone wrote an entire book on a relevant subject. Many of his examples have to do with the theft of books. From the 7th century B.C. –
Whoever steals this tablet, or inscribes his name next to mine, may [the gods] Ashur and Belit strike him down in their wrath and wrath, and may they extirpate his name and his posterity in the earth.
Deuteronomy provides the closes parallel to Revelation:
Now, O Israel, listen to the statutes and the judgments which I teach you to observe, that you may live, and go in and possess the land which the Lord God of your fathers is giving you. You shall not add to the word which I command you, nor take from it, that you may keep the commandments of the Lord your God which I command you when he hears the words of this curse . . . and every curse that is written in this book would settle on him, and the Lord would blot out his name from under heaven. (Deut 4:1-2, 20:19-20)
Rev. 22 also has its roots in the so-called integrity forms, that is, no one should twist what is written. 1 Enoch has echoes in Rev. For example, here in 104:10-11 –
And now I know this mystery: For they (the sinners) shall alter the just verdict and many sinners will take it to heart; they will speak evil words and lie, and they will invent fictitious stories and write out my Scriptures on the basis of their own words. And would that they had written down all the words truthfully on the basis of their own speech, and neither alter nor take away from my words, all of which I testify to them from the beginning!
These curses are found in the Middle East, Egypt, the Greco-Roman world, among the Jews, and the Christians. Here is a reference in the fathers of the 2nd century. In fact, it seems that Dionysius of Corinth is thinking about Rev 22 –
When the brethren asked me to write letters, I wrote them. And these the apostles of the Devil have filled full of tares, CUTTING SOME THINGS OUT AND PUTTING OTHERS IN. Woe is in store for these. Surely it is not surprising that some have eagerly desired to falsify even the Lord’s writings, when they have plotted against such inferior writings as mine. Found in Eusebius, History of the Church 4.23.12
“I, Jesus, have sent my angel to bear witness to you of these things…” says the conclusion of Revelation. In other words, let no one alter Revelation!
We should add that Rev 22:18-19 has nothing to do with the science of textual criticism. This is the search for the original, apostolic text of the Bible, including the book of Revelation. It doesn’t even teach that we should use only one version of the Bible.
NOTE: The early church, for two centuries more, said that the gift of prophecy was still active in the congregations. Contrary to common error, they did not believe that this contradicted their belief in a closed canon. Only the Montanist movement believed that the utterances of its prophets should be written as authoritative scripture. Please read my analysis here: Christian prophecy and canon in the second century: a response to B. B. Warfield – Open Our Eyes, Lord! (openoureyeslord.com)
“The canon is closed, but Rev 22 has nothing to do with it,” by Gary S. Shogren, Professor of New Testament, ESEPA Seminary, San Jose, Costa Rica
Open Our Eyes, Lord! 
What do you think?