Peter opens his big mouth at the end of Matthew chapter 19, asking Jesus (with seemingly mercenary intent) what the disciples get for giving up everything to follow Jesus. Jesus' reply offers both a word of encouragement (19:28-29) and a rebuke (v. 30). The rebuke, "But many who are first will be last, and many who are last will be first," reminds Peter that no one can put God in debt. God owes us nothing. Everything we receive comes from God by grace, and only those who put themselves (that is, recognize the reality that they are) last will ever receive God's blessing . . . a.k.a. "a great reversal."
Mathew provides 4 separate episodes in chapter 20 to illustrate the great reversal(s):
1) The Parable of the Workers in the Vineyard (1-16): In this parable, we learn what the Kingdom of God is like (v. 1). We know that the repeated line in verse 16 (an inclusio) tells us Jesus is still instructing Peter that God owes no one (cf. 19:30). Whether a worker works 1 hour or 12 hours, by God's sovereign authority, he can pay them whatever he wants. "The point of the parable is not that all in the Kingdom receive the same reward [though they do in this parable], but that Kingdom rewards depend on God's sovereign grace." Peter's attempt to curry favor with God through sacrificial service is just as much of an anathema as the religiosity of the Pharisees (Mt. 15:8-9). God's grace opposes all notions of desert, prominence, rich, morality, power, etc.
2) The Prediction of Death (20:17-19): To be honest, I'm not sure why Matthew put this prediction where he did. Is it to highlight the source of God's sovereign grace (referring back to vv. 1-16)? Is it designed to show a sharp contrast to the incident that follows? Regardless, I think Jesus' mention of being "raised to life" is the phrase that must have set the Zebedee clan to work. If Jesus' is going to be "raised," then they want to make sure they're in on the glory.
3) The Zebedee Request (20:20-28): James' and John's mom serves as the speaker for the delegation. She asks that her two boys get the highest seats of honor in the coming Kingdom. Jesus explains that the highest positions in the Kingdom involve a life of suffering, rejection, and pain (just like King Jesus, 20:22). Still they are willing to endure it. Jesus affirms that such a future awaits the naive disciples, and yet, Jesus does not promise any prominence for such efforts (see thoughts under #1). The whole conversation caused a stir among the other disciples (20:24); so much so that Jesus had to speak up. He warned them that the "Great Reversal" included worldly notions of leadership. In God's economy, real leadership requires sacrificial service. Real greatness is marked by the willingness to die for others, not by how many servants one has under their thumb. At this moment, Jesus reminds them that the Son of Man did not come to be served. O, the Son of Man had the right to demand servitude. But the gracious God does not get served by human hands (Acts 17:25). Instead, the Son of Man gives his life as a ransom for many (Mt. 20:28). He came to ransom (buy back) people out of slavery, sin, and death. The Son of Man became a slave to death that he might become the master of life.
4) The Blind See (20:19-34): This final story humorously shows the disciples (and us!) that it's the down-and-outers who often understand Jesus. The blind see Jesus as the merciful Son of David (20:30). They see Him as the Great Reverser. They cry out to Him. Jesus is compassionate and heals their physical blindedness. Then, they join Jesus; rag-tag team of followers, ready to serve and give their lives in service to others.
So too, we are to become like the blind men, not demanding or expecting glory, but simply turning to Christ for mercy and then joining Him in the ministry of mercy.