I tend to agree with David on this one. The language at Trent does not state no further books can be added. It just says “these are the books.” Granted, I see no sign of adding books in the future, but I would not say the canon has been dogmatically
“closed.” Rather the books named at Trent have been
dogmatically received as canonical Scripture.
Pertinent paragraph from Council of Trent — The sacred and holy, ecumenical, and general Synod of Trent,–lawfully assembled in the Holy Ghost, the Same three legates of the Apostolic Sec presiding therein,–keeping this always in view, that, errors being removed, the purity itself of the Gospel be preserved in the Church; which (Gospel), before promised through the prophets in the holy Scriptures, our Lord Jesus Christ, the Son of God, first promulgated with His own mouth, and then commanded to be preached by His Apostles to every creature, as the fountain of all, both saving truth, and moral discipline; and seeing clearly that this truth and discipline are contained in the written books, and the unwritten traditions which, received by the Apostles from the mouth of Christ himself, or from the Apostles themselves, the Holy Ghost dictating, have come down even unto us, transmitted as it were from hand to hand; (the Synod) following the examples of the orthodox Fathers, receives and venerates with an equal affection of piety, and reverence, all the books both of the Old and of the New Testament–seeing that one God is the author of both --as also the said traditions, as well those appertaining to faith as to morals, as having been dictated, either by Christ’s own word of mouth, or by the Holy Ghost, and preserved in the Catholic Church by a continuous succession. And it has thought it meet that a list of the sacred books be inserted in this decree, lest a doubt may arise in any one’s mind, which are the books that are received by this Synod. They are as set down here below: …(books listed here)… But if any one receive not, as sacred and canonical, the said books entire with all their parts, as they have been used to be read in the Catholic Church, and as they are contained in the old Latin vulgate edition; and knowingly and deliberately contemn the traditions aforesaid; let him be anathema. Let all, therefore, understand, in what order, and in what manner, the said Synod, after having laid the foundation of the Confession of faith, will proceed, and what testimonies and authorities it will mainly use in confirming dogmas, and in restoring morals in the Church.In Gary Michuta’s research for his book Why Catholic Bibles Are Bigger, he came across reference to the Council of Trent passing over “in silence” the canonical status of the book of Esdras, Fourth Ezra, and Third Maccabees. See his
article and reference here. Apparently the Council of Trent voted on whether or not they should explicitly reject these books. They ended up specifically voting to pass over these books “in silence.”
Again, to the OP, I see no sign of books being added. Also, books like Esdras, Fourth Ezra, and Third Maccabees are OT. So the evidence of the NT being closed is the lack of evidence that any other books are under consideration.