D.A. Carson believes Cana provides the bookends for a section running from 2:1-4:54 (Carson, The Gospel according to John (Pillar New Testament Commentary) , 166 . In that section, he believes the theme of old/new is being highlighted over and over again. As different as we see the Gospel of John from the synoptics this is actually an area of overlap as we see this same theme developed early in the Gospel of Mark.
In Mark 2 we also get the idea of old/new. Jesus heals a paralytic and forgives his sin. The response of the crowd, “We have never seen anything like this!” (Mark 2:12). Jesus is questioned about fasting and why Jesus’ disciples don’t do it. Jesus’ response, there is no fasting at weddings. Sound familiar? John 2 starts with the wedding at Cana and John 3 ends with John the Baptist talking about Jesus coming as the great bridegroom. Mark 2 talks about the old and new wineskins and closes with Jesus teaching about the Sabbath and its real intention. Out with the old, in with the new. In John 2 Jesus clears the temple and declares something new about the temple in reference to his own crucifixion. In John 3 we have “new birth” of water and spirit. In John 4 we have new worship, not at Gerizim or Jerusalem but worship that is done in spirit and in truth.
Jesus didn’t come to keep status quo. He came to set things right. The old way of doing things wasn’t sufficient because there was a better way that could only come through the final defeat of sin. Jesus gives us glimpses of what is coming throughout his ministry that climaxes with a cross, an empty tomb, and an invitation to all who believe to participate in the new life that comes through our status as children of God.