2 Peter 1:15

‘Yes, I will give diligence that at every time you may be able after my exodus to call these things to remembrance.'

He is concerned that after his death they would still continue to have in remembrance:

1) The divine power received through the knowledge of the One Who had called them by His glory and excellence (2 Peter 1:3).

2) That He has granted to them those great and precious promises which have resulted in their partaking of the divine nature (2 Peter 1:4).

3) The reality of their calling and election.

These three certainties, along with the resulting life that they are to lead as described in 2 Peter 1:5, will be the foundation of their future lives.

Some see here the promise of further written information from which they will be able to learn, and refer it to the writing of the Gospel of Mark. The idea is that the writing of it is already in progress, and he will speed it up so as to ensure that it is soon available for them. The fact of Peter's input into the Gospel of Mark is accepted by many scholars, and was testified to early on in the writings of Papias (mid-second century).

Note the use of the term ‘exodus' for death. Moses and Elijah had discussed Jesus' coming ‘exodus' on the Mount of Transfiguration (Luke 9:31). So as his mind turns towards the experience that he, James and John had had there he begins to align himself with his Master Whose glory had been revealed there. This sure touch reveals that this is Peter himself writing, especially in view of the fact that the description of the Transfiguration that follows is clearly independent of the Gospels.