Matthew 16 is clearly saying
[27] For the Son of man shall come in the glory of his Father with his angels: and then will he render to every man according to his works. [28] Amen I say to you, there are some of them that stand here, that shall not taste death, till they see the Son of man coming in his kingdom.In Matthew 16:13-20 Peter has shown understanding of Jesus’ identity, that he is the Christ (Messiah). This experience is to help deepen this understanding. It is so special that only Jesus’ three closest followers - Peter, James and John - are chosen to witness it. Jesus wants them to understand that his role of Messiah will involve suffering and death, but this will not be the final outcome of his mission. Jesus has come from Heaven and he will return there when he has completed his task on Earth.
In Matthew this is in chapter 17 immediately after the above "[27] For the Son of man shall come in the glory of his Father with his angels: and then will he render to every man according to his works."
And in any case, the Olivet discourse is about the destruction of the temple in 70 AD
I appreciate your comments, Cronos. Have you ever considered that Mt. 25 is the judgment Jesus talked about in Mt. 16?