Don’t know how to put it any plainer, The Bible doesn’t specifically say that public Revelation is closed. Protestants believe public Revelation is closed, despite the fact that it isn’t specifically said in the Bible.
Found this article on
cybercatholics.com that explains it in better words than I ever could:
How do we know that public Revelation has ended?
Similarly, Holy Scripture never unequivocally states that public Revelation from God,
binding on the consciences of all His children, has ever ended. How do we know that
Revelation, that is, God’s self-disclosure in Jesus Christ through the Holy Spirit, came to
an end with the death of the last Apostle? We know because the Church tells us so,
because our ancestors in the faith believe it and the successors to the Apostles so declared
it.
**Based on Sola Scriptura, Protestants cannot close the canon. Oh, they can accept
precedent or the words of the Reformers to that effect, but the Reformers were sticking to
the classical Catholic canon with little explanation as to when and how exactly public
revelation ended.**The fact that Sola Scriptura allows for open-ended revelation has not been ignored by
myriads of sects, from Montanism way back in Tertullian’s time to the ecstatic sects of
the Middle Ages to Seventh-day Adventism and Mormonism—this last one even has
three more books of “sacred scriptures” besides the Bible! But this glaring contradiction
has been passed over in silence by Protestant apologists.
A Protestant, if he or she is to be consistent, can’t criticize others who add their
revelations to the Bible simply because the Bible is silent on the subject. The answer to
this dilemma comes from outside the Bible, from the all-encompassing Tradition
maintained, treasured, and explained within the One, Holy, Catholic, and Apostolic
Church.