That prophecy is fulfilled from that precise moment and it is similar to another prophecy ("Truly, I say to you, there are some standing here who will not taste death until they see the kingdom of God after it has come with power") of Jesus addressed to disciples, and who if not the Best Disciple (Joseph "from Arimathea") could have a so strong apocalypticist faith in the coming of the kingdom during his same life?
But then if that prophecy is fulfilled from that precise moment, the divine Christ has already abandoned from that precise moment the body of Jesus, and therefore it is the Christ (not Jesus) who is already seen from that moment (by who has "eyes to see" among the audience of Jesus in that precise moment: the only Joseph of Arimathea, not coincidentially a PHARISEE) returned to his original divine state:
Just since he knows that the Christ, once abandoned Jesus in Mark 14:62, is already coming down on the clouds of heaven, then Joseph buried Jesus to give him a second birth in view of the coming general Resurrection of the Dead."sitting at the right hand of the Mighty One and coming on the clouds of heaven".
This interpretation is so simple that it explains alone:
1) why Joseph is pharisee
2) why Joseph comes from Arimathea
3) why the Generation-Prophecy is addressed to only disciples
4) why the first readers of Mark were separationists according to Irenaeus
5) why Joseph is expecting the kingdom
6) why Jesus is beaten only after that Christ has abandoned him in 14:62.
7) why what happens after 14:62 and before the burial there are two/three episodes (Barabbas, the Cyrenaic, the two robbers) designed to secure the readers that the man Jesus was the Christ even after 14:62, against the original separationism of proto-Mark.