It is in regard to this [your entrance in God's kingdom] that I fully intend from now on to keep on reminding you of these things, even though you [already] know them and are established in their unveiled truth.
And it is right that I consider it in this way, for as long as I am [dwelling] in this tent, I will stir you up by way of reminded, knowing that I am shortly to lay this tent aside as indeed Our Lord, Jesus Christ, made clear to me.
So I am taking each and every opportunity to ensure that you will have at hand a perpetual aide memoire of these things..
The letter writer makes a clean breast of it. It is almost as if he is saying something like,
"Well I know you must be wondering why I should be writing again, but let me be utterly frank with you. I have no choice about this. This is what I am called to do. This is my task."
And we also know that these letters are written not just for one or other group in one or other location. They were sent out - and the message is such that it would be quite in line with what Peter writes for copies to be made for further distribution.
The important part of this excerpt is the phrase:
I am shortly to lay aside this tent as indeed Our Lord, Jesus Christ, made clear to me.
This has a strong echo of the account given by John of Peter's conversation with Jesus that we find at the conclusion of John's Gospel. With this we begin to see that Peter is involved in the same matter which the Apostle had discussed when he described the meeting of the disciples with their risen Lord back on the shores of Lake Galilee.
You will recall that it was there that Jesus has restored Peter and had begun to explain to him what His resurrection would mean not just for Peter's friendship with the Son of God, but also for Peter's service for the sheep for whom the Good Shepherd had lain down His life.
Clearly, It was probably initially spoken in Aramaic and this letter as well as John's gospel (and the other gospels) were written in popular Greek - the variant use of AGAPAS and PHILEIS suggests that Jesus was helping Peter to appreciate that He, the Lord, was not going to be persuaded that Peter couldn't be His under-shepherd. Peter would indeed be able to feed the Lord's sheep because he was indeed the recipient of the Lord's special love. At that time Peter may have not comprehended what Jesus was saying. But this was the beginning of his learning curve. We can sense Peter's learning from what he has previously written, in his first letter:
Having purified your life by obedience to the truth for a sincere love of the brethren (PHILADELPHIAN), earnestly from the heart love (AGAPESETE) one another (1 Peter 1:22).
and also just before this where he has creatively encouraged his readers to participate in a full flowering of the kinds of characteristics that God has showered upon them in His Son.
... and to integrity add brotherly kindness (PHILADELPHIAN) and to brotherly kindness add love (AGAPE) (2 Peter 1:7).
So, it would seem that the Apostle's source for this complex conversation is none other than Peter himself. It is as if John is recounting Peter's own account of his difficulty in appreciating the kindness of the Lord Jesus toward him. And this record includes Jesus' prophecy concerning the kind of death by which Peter was to glorify God (21:19).
I tell you this in solemn truth that when you were young you tightened your belt and walked abroad wherever you wanted to go, but when you grow old, you will stretch out your hands and find another binding you to carry you off where you do not want to go. And this He said to indicate the kind of death by which Peter would glorify God. And having said this He said to Him: Follow me!
Here Jesus confirmed to Peter, that yes, his previous willingness to lay down his life for Him (13:37) was accepted; that indeed would come to pass. And so, in saying "Follow me!", Jesus was re-issuing the call He had made on that same shore some years back (Mark 1:16-20). That was just after he had called John and James, the sons of Zebedee.
And having heard these words about his own life and death, Peter turned and asked a question about John and that was when the Lord specifically addressed Peter's distraction from the profundity of what he had just been told. The important thing was re-specified:
You follow me!
The record is set straight. The Lord's reply redirected Peter's distraction. This was no prophecy about John's longevity. How did that rumour come about? We can guess that, for a while, Peter may have been confused by Jesus' reply, but the long-term impact of what Jesus had said to him certainly proved effective. Both john and Peter stood in need of being assured by the One who had been resurrected. Their hope in life and in death would be in the resurrected one who now sits at God's right hand! And it is in that hope that Peter stirs up his readers with this second letter. Jesus had told him:
You follow me!
and so this letter was one outcome of that command.