2 Peter 1:16-18 indicates that the Transfiguration was a Model of the Parousia.

The fact that Jesus was expected to appear in the radiant glory of His post-ascension resurrection body at the time of the parousia is also implied in 2 Peter 1:16-18:

For we did not follow cleverly devised tales when we made known to you the power and coming [parousia] of our Lord Jesus Christ, but we were eyewitnesses of His majesty.  For when He received honor and glory from God the Father, such an utterance as this was made to Him by the Majestic Glory, ‘This is My beloved Son with whom I am well-pleased’— and we ourselves heard this utterance made from heaven when we were with Him on the holy mountain.

2 Peter 1:16-18 is a description of the transfiguration.  During the transfiguration, Jesus appeared to the disciples in the likeness of a being of light. (Matthew 17, Mark 9, Luke 9)  What is interesting about this description of the transfiguration is that the Greek word translated coming in v. 16 is parousia, the same word often used to refer to the second coming throughout the New Testament.  The fact that Peter uses the word parousia to describe the moment in which Jesus was transformed into a being of light implies that Peter may have seen the transfiguration as a visionary shadow or model of the parousia, the second coming.  The fact that the transfiguration in which Jesus appeared in bright, radiant glory may be a kind of model of the second coming seems to be confirmed by Yosippon’s description of the fiery army in the clouds of A.D. 66.  At this time Jesus appeared in fiery radiance in the clouds of heaven bearing the same luminescent likeness of His body at the transfiguration in confirmation of 2 Peter 1:16-18.

It should also be noted that this is not the only way in which the transfiguration was a model of the second coming.  According to Matthew 17:5 the Glory Cloud also appeared in the midst of the transfiguration: “While he was still speaking, a bright cloud overshadowed them, and behold, a voice out of the cloud said, ‘This is My beloved Son, with whom I am well-pleased; listen to Him!’”  This bright cloud is the Glory Cloud, the quintessential sign of the presence of God.  For historical evidence of the presence of the Glory Cloud in A.D. 68 and A.D. 70 see The Appearance of Christ in A.D. 68? and The Coming of Christ in A.D. 70–Like You’ve Never Heard it Before!.