Did the Apostles know they were writing Scripture?

Don'kno says:

Hi, I rely on Jesus, not man. When Paul rightly quoted "All Scripture is given by inspiration of God" He couldn't have been talking about his own letters as scripture, they hadn't been canonized yet. He was talking about the law and the prophets and the writings. If you want to know the truth go to the one who is the truth. Go to God not man.

 I answer:

What did St. Peter mean when he said about Pauline writings:

2 Peter 3:15-17
King James Version (KJV)
15 And account that the longsuffering of our Lord is salvation; even as our beloved brother Paul also according to the wisdom given unto him hath written unto you;
16 As also in all his epistles, speaking in them of these things; in which are some things hard to be understood, which they that are unlearned and unstable wrest, as they do also the other scriptures, unto their own destruction.
17 Ye therefore, beloved, seeing ye know these things before, beware lest ye also, being led away with the error of the wicked, fall from your own stedfastness.

Sounds to me as though St. Peter counts St. Paul's writings among the Scriptures.  Now let's see what he says about the other Apostles:

2 Peter 1
King James Version (KJV)
¹³ Yea, I think it meet, as long as I am in this tabernacle, to stir you up by putting you in remembrance;¹⁴ Knowing that shortly I must put off this my tabernacle, even as our Lord Jesus Christ hath shewed me.¹⁵ Moreover I will endeavour that ye may be able after my decease to have these things always in remembrance.¹⁶ For we have not followed cunningly devised fables, when we made known unto you the power and coming of our Lord Jesus Christ, but were eyewitnesses of his majesty.¹⁷ For he received from God the Father honour and glory, when there came such a voice to him from the excellent glory, This is my beloved Son, in whom I am well pleased.¹⁸ And this voice which came from heaven we heard, when we were with him in the holy mount.¹⁹ We have also a more sure word of prophecy; whereunto ye do well that ye take heed, as unto a light that shineth in a dark place, until the day dawn, and the day star arise in your hearts:²⁰ Knowing this first, that no prophecy of the scripture is of any private interpretation.²¹ For the prophecy came not in old time by the will of man: but holy men of God spake as they were moved by the Holy Ghost.

Yeah, I'm pretty certain that the Apostles knew they were writing Scripture:

2 Corinthians 3:6
King James Version (KJV)
⁶ Who also hath made us able ministers of the new testament; not of the letter, but of the spirit: for the letter killeth, but the spirit giveth life.

Sincerely,

De Maria