This question was asked and answered in an older Watchtower magazine. The take away is that those apostles who lived to see Jesus coming in his kingdom were the apostles Peter,James and John who witnessed the transfiguration.
About a week after saying what he did at Matthew 16:28, Jesus took “some of” the apostles (Peter, James and John) up on a lofty mountain, likely Mount Hermon. There he was transfigured to appear in a vision with Moses and Elijah. And God said: “This is my Son, the one that has been chosen. Listen to him.” —Luke 9:28-35; Matt. 17:1-5; Mark 9:2-6. The transfiguration was a vision of Jesus in Kingdom power and heavenly glory, as Peter later confirmed. Referring to the transfiguration, Peter explained that they had thus “become eyewitnesses of his magnificence.” He added that in the transfiguration Jesus had “received from God the Father honor and glory.” (2 Pet. 1:16-18) So, it appears that when Jesus said that before they died some of the apostles would see him in his kingdom, he was referring to the transfiguration scene that some of them witnessed shortly afterward.
Additional discussion ifof this event is found here.