May you have peace!
What were the scriptures to which Paul referred in 2 Timothy 3:16, viz, "All Scripture is inspired of God, ..." ?
At the time, Paul was referring to "Moses, the Psalms, and the Prophets" (please see Luke 24:27, 32, 44, 45), which did NOT include the histories of the Israelite kings (1 and 2 Kings), the chronologies of Israelite lineage (1 and 2 Chronicles), and the "wisdom" of Solomon/Lemuel (Proverbs, Ecclesiastes).
He could only be referencing OT writings, correct?
Correct.
What establishes the weight and divine authority of the NT, as Paul could not logically be speaking of future writings?
Actually, with the exception of the Revelation and John's gospel account, there really is none. "Scripture" is that which is written while men are "in spirit" (inspired) and "borne along" (guided) by the Holy Spirit, Christ, who TOLD them to write what they did. Hence, the Revelation and John's account of the gospel are "scripture." The other gospels, epistles (letters of Paul, Peter, John, Jude and James, to various congregations, persons and groups), and the Acts of the Apostles were not "inspired" and, therefore, are not scripture.
That is not to say that there is NO wisdom in the other writings; truly, there is some... but what is there, whether inspired or not... is for unbelievers... not believers.
How would one who accepts the Bible understand this?
Actually, the PROBLEM with most who claim to be "christian"... and/or those who "accept" the Bible... is just that: their faith in the Bible... VERSUS in the One about whom the Bible bears witness:
"You are searching the scriptures because you THINK... that by means of THEM... you WILL have everlasting life. And these are the very ones... that bear witness... ABOUT ME... and yet... you do not WANT to come... TO ME... that you might HAVE life." John 5:39, 40
Because SO many put their faith IN THE BIBLE... rather than IN THE ONE about whom the Bible bears witness... they are easily misled due to all of the interpretations, misinterpretations, translations, mistransliterations, tampering, omissions, errors, inclusion, additions, commentaries, contradictions, and versions. I am not judging: I was among these.
I have since learned and hope that these, too, will one day learn, that if they would only put their faith IN CHRIST... and GO TO HIM... the SOURCE of ALL TRUTH... they would not NEED the Bible. That is because, as Christ, the ONE ABOUT WHOM THE BIBLE BEARS WITNESS is recorded to have said... THE HOLY SPIRIT...(and NOT "the Bible")... WILL LEAD YOU... INTO ALL TRUTH.
Unfortunately, because they cannot SEE the Holy Spirit, Christ, with their eyes of flesh... they continue to put their faith in an idol, a "golden calf," a VISIBLE REPRESENTATION... of God/Christ on earth. They lack the faith to BELIEVE... and thus, they are UNbelievers and so need to "see it in writing."
I hope this helps and, again, I bid you peace.
A slave of Christ,
SA