Some standing here will not taste death

27 For the Son of Man is going to come with his angels in the glory of his Father, and then he will repay each person according to what he has done. 28 Truly, I say to you, there are some standing here who will not taste death until they see the Son of Man coming in his kingdom (Mt 16:27-28). 

12 Then I turned to see the voice that was speaking to me, and on turning I saw seven golden lampstands, 13 and in the midst of the lampstands one like a son of man, clothed with a long robe and with a golden sash around his chest. 14 The hairs of his head were white, like white wool, like snow. His eyes were like a flame of fire, 15 his feet were like burnished bronze, refined in a furnace, and his voice was like the roar of many waters. 16 In his right hand he held seven stars, from his mouth came a sharp two-edged sword, and his face was like the sun shining in full strength.20 As for the mystery of the seven stars that you saw in my right hand, and the seven golden lampstands, the seven stars are the angels of the seven churches, and the seven lampstands are the seven churches (Rev 1:12-16,20).

Mt 16:28 is a familiar "problem passage." Did Jesus mispredict the future? 

It's instructive to compare the Matthean prediction with Rev 1. John was one of the disciples whom Jesus addressed on that occasion (in Mt 16). Before John died, Jesus came to him. His appearance is glorious. There's even the angelic motif. Jesus comes with angels (i.e. stars=angels). 

This is a personal appearance. But it is, of course, distinct from the Second Coming–which is a global, one-time, endtime event. So John did not taste death until he saw Jesus come to him, in royal imagery that parallels the Matthean prediction. (By the same token, Jesus came to Paul [Acts 9, 22, 26], to instigate his conversion.)

Likewise, in his dictated letters to the seven churches (Rev 2-3), Jesus threatens to "come" to some of them in judgment. But in context, that hardly seems to be the end of the world. It simply marks the demise of that particular fellowship. 

We need to distinguish at least two different ways in which Jesus can come to people. There's a local, individualized appearance, and then there's a global return. Both are personal. But the former is repeatable whereas the latter is climactic. Between Jesus coming within church history (i.e. objective visions) and Jesus coming at the end of church history (i.e. the return of Christ). 

Some Protestants misunderstand sola scriptura. They treat the Bible as an encyclopedia. Unless they can find something in Scripture, it never happened. This often leads to very creative prooftexting. But the Bible does not intend or pretend to record everything that exists. 

Jesus may well have appeared to other disciples in the same way he appeared to John. It's just that John wrote about it.