Where's the fulfillment of Mark 10:39?

In my last post, I referred to how John 21:18-19 lines up well with what other sources report about Peter and Mark's use of Peter as a source. Something similar can be said of the apostle John, but with another element that adds further credibility to what's reported about him.

Matthew 20:23 and Mark 10:39 refer to how James and John, the sons of Zebedee, will drink the cup Jesus will drink. Drinking the cup refers to suffering, probably including martyrdom. Jesus' death is mentioned multiple times in the nearby context in both gospels (Matthew 20:18-19, 20:28, Mark 10:33-34, 10:45). Jesus associates his cup of suffering with his death (Matthew 26:27-28, 26:39, Mark 14:23-24, 14:36). In the second century, Polycarp makes a comment that's relevant to how we interpret the language in question. Since he was a disciple of John, Polycarp's interpretation of the cup terminology has some added significance. In the context of addressing his own martyrdom, Polycarp commented:

"I give You [God the Father] thanks that You have counted me worthy of this day and this hour, that I should have a part in the number of Your martyrs, in the cup of Your Christ" (The Martyrdom Of Polycarp 14)

Jesus died early as a martyr. So did James. But there's no mention of John's death as a martyr. Instead, he's referred to as still alive several chapters into Acts and in Galatians 2. Five New Testament documents are attributed to him, his reference to himself as "the elder" in two of them (2 John 1, 3 John 1) makes the most sense if he lived to an old age, the internal evidence for the date of Revelation supports a later rather than earlier date, and later sources agree that John lived to an old age.

So, we have a large number and variety of independent lines of evidence converging in support of the conclusion that John lived well past the time when Jesus and James died. John seems to have lived to the late first or early second century. I've argued elsewhere that he probably died as a martyr at that point. But none of the earliest sources refer to his martyrdom, unlike the early references to the martyrdom of Jesus and James.

It's not just that so many sources agree that John lived so long. It's also that they agreed about that fact in spite of having some incentive to claim otherwise. Assigning an early martyrdom to John would provide a fulfillment of Mark 10:39 and the best type of fulfillment. Instead, he's referred to as living an unusually long life, and not much is said about his martyrdom. That's probably because he did live so long, and the early Christians weren't as careless or dishonest as they're often made out to be.